CN203894464U - Imaging lens and imaging equipment - Google Patents

Abstract

In order to achieve a small size, low cost, a wide field angle and a high performance in an imaging lens, and eliminate the limits on a used imaging device, the utility model discloses an image lens (1) which consists of a first negative lens (L1), a second negative lens (L2), a third positive lens (L3), a fourth positive lens (L4), a fifth negative lens (L5), and a sixth positive lens (L6), wherein the above six lenses are basically arranged from an object side sequentially. The radius of curvature of an object side surface of the fourth lens (L4) is R8, and the radius of curvature of an image side surface of the fourth lens (L4) is R9. When the abbe number of the material of the third lens (L3) relative to a d line is vd3, and the abbe number of the material of the fifth lens (L5) relative to a d line is vd5, the following formulas (1) and (6) are met: (1), -0.61<(R8+R9)/(R8-R9)<0.44...; and (6), 38.1<vd3+vd5<45.1....

Description

Imaging lenses and imaging equipment

technical field

The present invention relates to an imaging lens and an imaging lens device. More specifically, the present invention relates to imaging lenses suitable for use in in-vehicle cameras employing imaging devices such as CCD (Charge Coupled Device) and CMOS (Complementary Metal Oxide Semiconductor), cameras for mobile terminals, surveillance cameras, etc. . Further, the present invention relates to an imaging device including the imaging lens. the

Background technique

Recently, imaging devices such as CCDs and CMOSs have become very small, and the resolution of imaging devices has become very high. Therefore, the size of the body of an imaging apparatus including such an imaging device becomes small. Therefore, in addition to the excellent optical performance of the imaging lens, there is a need to reduce the size of the imaging lens to be mounted on the imaging device. Meanwhile, lenses mounted on in-vehicle cameras, surveillance cameras, etc. need to be able to be constructed with a small size and low cost, and to achieve a wide angle of view and high performance. the

The following Patent Documents 1 to 16 disclose lens systems composed of six lenses. This lens system is used in a camera on which a small-sized CCD is mounted, and uses a plastic aspherical lens. the

Related technical literature

Patent Documents

Patent Document 1:

Japanese Unexamined Patent Publication No.2005-221920

Patent Document 2:

Japanese Unexamined Patent Publication No.2006-171597

Patent Document 3:

Japanese Unexamined Patent Publication No.2006-349920

Patent Document 4:

Japanese Unexamined Patent Publication No.2007-164079

Patent Document 5:

Japanese Unexamined Patent Publication No.2007-249073

Patent Document 6:

Japanese Unexamined Patent Publication No.2008-134494

Patent Document 7:

Japanese Unexamined Patent Publication No.2010-243709

Patent Document 8:

Japanese Patent No.2599312

Patent Document 9:

Description of U.S. Patent No.7023628

Patent Document 10:

Description of U.S. Patent No.7768719

Patent Document 11:

Description of U.S. Patent No.7933078

Patent Document 12:

Japanese Unexamined Patent Publication No.2010-160479

Patent Document 13:

Japanese Unexamined Patent Publication No.2008-76716

Patent Document 14:

Japanese Unexamined Patent Publication No.2009-92797

Patent Document 15:

Japanese Unexamined Patent Publication No.2009-92798

Patent Document 16:

Japanese Unexamined Patent Publication No.2010-009028

Contents of the invention

Meanwhile, requirements for imaging lenses to be mounted on in-vehicle cameras, surveillance cameras, etc. are becoming more stringent every year. Therefore, it is necessary to reduce the size and cost of the imaging lens, which has a wider field of view and higher performance. the

Here, the lens systems disclosed in Patent Documents 1, 2, 4, 8, 9, and 11 are good for chromatic aberration and sensitivity because cemented lenses are used. However, a dedicated adhesive material and handling are required depending on the usage conditions of the lens system, and the cost is increased. In the lens system disclosed in Patent Document 3, the half angle of field is 40°. or less, which is not wide enough to achieve the wide field of view to be solved by the present invention. Further, the lens system disclosed in Patent Document 10 is an anamorphic lens (anamorphic_lens). Therefore, the lens system cannot be manufactured at low cost. the

In view of the foregoing, an object of the present invention is to provide an imaging lens capable of achieving small size, low cost, wide angle of view, and high performance, and an imaging device including the imaging lens. the

The imaging lens according to the first aspect of the present invention is an imaging lens basically composed of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, The negative fifth lens and the positive sixth lens are composed of six lenses,

Wherein the following conditional formulas (1) and (6) are satisfied:

-0.61<(R8+R9)/(R8-R9)<0.44...(1); and

38.1<vd3+vd5<45.1...(6), where

R8: radius of curvature of the object-side surface of the fourth lens,

R9: radius of curvature of the image side surface of the fourth lens,

vd3: the Abbe number of the material of the third lens with respect to the d-line, and

vd5: the Abbe number of the material of the fifth lens with respect to the d line. the

The imaging lens according to the second aspect of the present invention is an imaging lens basically composed of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, The negative fifth lens and the positive sixth lens are composed of six lenses,

Wherein the following conditional formulas (1-1) and (12) are met:

-0.11<(R8+R9)/(R8-R9)...(1-1); and

R9/f<-2.9...(12), where

R8: radius of curvature of the object-side surface of the fourth lens,

R9: the radius of curvature of the image-side surface of the fourth lens, and

f: focal length of the whole system. the

An imaging lens according to a third aspect of the present invention is an imaging lens basically composed of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, The negative fifth lens and the positive sixth lens are composed of six lenses,

Wherein the following conditional formulas (1-2) and (4) are satisfied:

-0.075<(R8+R9)/(R8-R9)<0.11...(1-2); and

-1.04<(R10+R11)/(R10-R11)<-0.34...(4), where

R8: radius of curvature of the object-side surface of the fourth lens,

R9: radius of curvature of the image side surface of the fourth lens,

R10: the radius of curvature of the object-side surface of the fifth lens, and

R11: radius of curvature of the image-side surface of the fifth lens. the

An imaging lens according to a fourth aspect of the present invention is an imaging lens basically composed of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, The negative fifth lens and the positive sixth lens are composed of six lenses,

wherein the object-side surface of the third lens is concave, and

Wherein the following conditional formulas (1-3) and (4-1) are satisfied:

(R8+R9)/(R8-R9)<0.17...(1-3); and

(R10+R11)/(R10-R11)<-0.35...(4-1), where

R8: radius of curvature of the object-side surface of the fourth lens,

R9: radius of curvature of the image side surface of the fourth lens,

R10: the radius of curvature of the object-side surface of the fifth lens, and

R11: radius of curvature of the image-side surface of the fifth lens. the

An imaging lens according to a fifth aspect of the present invention is an imaging lens basically composed of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, The negative fifth lens and the positive sixth lens are composed of six lenses,

wherein the object-side surface of the third lens is concave, and

where the fourth lens is a biconvex lens, and

where the fifth lens is a biconcave lens, and

Wherein the following conditional formulas (1-3) and (4-1) are satisfied:

(R8+R9)/(R8-R9)<0.17...(1-3); and

(R10+R11)/(R10-R11)<-0.35...(4-1), where

R8: radius of curvature of the object-side surface of the fourth lens,

R9: radius of curvature of the image side surface of the fourth lens,

R10: the radius of curvature of the object-side surface of the fifth lens, and

R11: radius of curvature of the image-side surface of the fifth lens. the

The expression "consisting essentially of six lens groups" means that in addition to these six lenses, lenses not having any refractive power, optical elements other than lenses, such as aperture stops and cover glasses, mechanical parts such as Lens flange, lens barrel, imaging device, camera hand shake blur correction mechanism, etc. the

The imaging lenses according to the first to fifth aspects of the present invention are basically composed of six lenses. Therefore, excellent optical performance can be obtained. Further, since the number of lenses is reduced, it is possible to reduce the size of the imaging lens and suppress the cost of the imaging lens. the

In the present invention, when the lens includes an aspherical surface, unless otherwise specified, the surface shape of the lens, such as convex, concave, flat, biconcave, meniscus, biconvex, plano-convex, and flat-concave, is considered in the paraxial region, And the sign of the refractive power of the lens, such as positive lens and negative lens. Further, in the present invention, the sign of the radius of curvature is positive when the surface shape is convex toward the object side, and negative when the surface shape is convex toward the image side. the

In the imaging lenses according to the first to fifth aspects of the present invention, it is desirable that the following conditional formulas (19) to (23) are satisfied. As an ideal mode, the imaging lens can include a structure in the following conditional formulas (19) to (23), or a combination of any two or more of them:

1<(D4+D5)/f<6...(19);

-1<f/R5<1...(20);

-3<f/R3<3...(21);

-30<f23/f<-3...(22); and

2<f45/f<25...(23), where

D4: the air gap between the second lens and the third lens on the optical axis,

D5: Central thickness of the third lens,

f: focal length of the whole system,

R5: radius of curvature of the object-side surface of the third lens,

R3: radius of curvature of the object-side surface of the second lens,

f23: the combined focal length of the second and third lenses, and

f45: The combined focal length of the fourth lens and the fifth lens. the

An imaging device of the present invention includes at least one of the first to fifth imaging lenses of the present invention. the

According to the imaging lens in the first aspect of the present invention, the arrangement of refractive power and the like in the entire system are appropriately set in the lens system including at least six lenses. And, conditional formulas (1) and (6) are satisfied. Therefore, small size, low cost, and wide angle of view can be realized. Further, it is possible to realize an imaging lens having high optical performance in which various aberrations are excellently corrected, and high-quality images can be obtained even in the peripheral portion of the image forming region. the

According to the imaging lens in the second aspect of the present invention, the arrangement of refractive power and the like in the entire system are appropriately set in the lens system including at least six lenses. And, conditional formulas (1-1) and (12) are satisfied. Therefore, small size, low cost, and wide angle of view can be realized. Further, it is possible to realize an imaging lens having high optical performance in which various aberrations are excellently corrected, and high-quality images can be obtained even in the peripheral portion of the image forming region. the

According to the imaging lens in the third aspect of the present invention, the arrangement of refractive power and the like in the entire system are appropriately set in the lens system including at least six lenses. And, conditional formulas (1-2) and (4) are satisfied. Therefore, small size, low cost, and wide angle of view can be realized. Further, it is possible to realize an imaging lens having high optical performance in which various aberrations are excellently corrected, and high-quality images can be obtained even in the peripheral portion of the image forming region. the

According to the imaging lens in the fourth aspect of the present invention, the arrangement of refractive power in the entire system, the surface shape of the third lens, and the like are appropriately set in the lens system including at least six lenses. And, conditional formulas (1-3) and (4-1) are satisfied. Therefore, small size, low cost, and wide angle of view can be realized. Further, it is possible to realize an imaging lens having high optical performance in which various aberrations are excellently corrected, and high-quality images can be obtained even in the peripheral portion of the image forming region. the

According to the imaging lens in the fifth aspect of the present invention, the arrangement of the refractive power in the entire system, the surface shapes of the third lens, the fourth lens, the fifth lens, etc. are appropriately set in the lens system including at least six lenses. And, conditional formulas (1-3) and (4-1) are satisfied. Therefore, small size, low cost, and wide angle of view can be realized. Further, it is possible to realize an imaging lens having high optical performance in which various aberrations are excellently corrected, and high-quality images can be obtained even in the peripheral portion of the image forming region. the

The imaging device of the present invention includes the imaging lens of the present invention. Therefore, the imaging device can be constructed with a small size and low cost. Further, the imaging device can perform shooting with a wide angle of field and obtain high-quality images with high resolution. the

Description of drawings

Fig. 1 is a schematic diagram illustrating the structure and optical path of an imaging lens according to an embodiment of the present invention;

Fig. 2 is a schematic diagram for explaining the surface shape of the second lens etc.;

3 is a cross-section illustrating a lens structure of an imaging lens in Example 1 of the present invention;

4 is a cross-section illustrating a lens structure of an imaging lens in Example 2 of the present invention;

5 is a cross-section illustrating a lens structure of an imaging lens in Example 3 of the present invention;

6 is a cross-section illustrating a lens structure of an imaging lens in Example 4 of the present invention;

7 is a cross-section illustrating a lens structure of an imaging lens in Example 5 of the present invention;

8 is a cross-section illustrating a lens structure of an imaging lens in Example 6 of the present invention;

9 is a cross-section illustrating a lens structure of an imaging lens in Example 7 of the present invention;

10 is a cross-section illustrating a lens structure of an imaging lens in Example 8 of the present invention;

11 is a cross-section illustrating a lens structure of an imaging lens in Example 9 of the present invention;

12 is a cross-section illustrating a lens structure of an imaging lens in Example 10 of the present invention;

13 is a cross-section illustrating a lens structure of an imaging lens in Example 11 of the present invention;

14 is a cross-section illustrating a lens structure of an imaging lens in Example 12 of the present invention;

15 is a cross-section illustrating a lens structure of an imaging lens in Example 13 of the present invention;

16 is a cross-section illustrating a lens structure of an imaging lens in Example 14 of the present invention;

17 is a cross-section illustrating a lens structure of an imaging lens in Example 15 of the present invention;

18 is a cross-section illustrating a lens structure of an imaging lens in Example 16 of the present invention;

19 is a cross-section illustrating a lens structure of an imaging lens in Example 17 of the present invention;

20 is a cross-section illustrating a lens structure of an imaging lens in Example 18 of the present invention;

21 is a cross-section illustrating a lens structure of an imaging lens in Example 19 of the present invention;

Fig. 22 (A) to Fig. 22 (D) are the aberration schematic diagrams of the imaging lens in example 1 of the present invention;

Fig. 23 (A) to Fig. 23 (D) are the aberration schematic diagrams of the imaging lens in the example 2 of the present invention;

Fig. 24 (A) to Fig. 24 (D) are the aberration schematic diagrams of the imaging lens in example 3 of the present invention;

Fig. 25 (A) to Fig. 25 (D) are the aberration schematic diagrams of the imaging lens in example 4 of the present invention;

Fig. 26 (A) to Fig. 26 (D) are the aberration schematic diagrams of the imaging lens in example 5 of the present invention;

Fig. 27 (A) to Fig. 27 (D) are the aberration schematic diagrams of the imaging lens in example 6 of the present invention;

Fig. 28 (A) to Fig. 28 (D) are the aberration schematic diagrams of the imaging lens in the example 7 of the present invention;

Fig. 29 (A) to Fig. 29 (D) are the aberration schematic diagrams of the imaging lens in the example 8 of the present invention;

Fig. 30 (A) to Fig. 30 (D) are the aberration schematic diagrams of the imaging lens in the example 9 of the present invention;

Fig. 31 (A) to Fig. 31 (D) are the aberration schematic diagrams of the imaging lens in example 10 of the present invention;

Fig. 32 (A) to Fig. 32 (D) are the aberration schematic diagrams of the imaging lens in the example 11 of the present invention;

Fig. 33 (A) to Fig. 33 (D) are the aberration schematic diagrams of the imaging lens in the example 12 of the present invention;

Fig. 34 (A) to Fig. 34 (D) are the aberration schematic diagrams of the imaging lens in the example 13 of the present invention

Fig. 35 (A) to Fig. 35 (D) are the aberration schematic diagrams of the imaging lens in the example 14 of the present invention;

Fig. 36 (A) to Fig. 36 (D) are the aberration schematic diagrams of the imaging lens in example 15 of the present invention;

Fig. 37 (A) to Fig. 37 (D) are the aberration schematic diagrams of the imaging lens in example 16 of the present invention;

Fig. 38 (A) to Fig. 38 (D) are the aberration schematic diagrams of the imaging lens in the example 17 of the present invention;

Fig. 39 (A) to Fig. 39 (D) are the aberration schematic diagrams of the imaging lens in the example 18 of the present invention;

Fig. 40 (A) to Fig. 40 (D) are the aberration schematic diagrams of the imaging lens in the example 19 of the present invention; And

FIG. 41 is a schematic diagram for explaining the configuration of an imaging apparatus for in-vehicle use according to an embodiment of the present invention. the

Detailed ways

Embodiments of the present invention will be described in detail with reference to the accompanying drawings. the

[Example of imaging lens]

First, an imaging lens according to an embodiment of the present invention will be described with reference to FIG. 1 . FIG. 1 is a schematic diagram illustrating the structure and optical path of an imaging lens 1 according to an embodiment of the present invention. The imaging lens 1 illustrated in FIG. 1 corresponds to the imaging lens in Example 1 of the present invention which will be described later. the

In Fig. 1, the left side is the object side and the right side is the image side, and the paraxial ray 2 from an object point at infinity and the off-axis ray 3, 4 at the full field angle 2ω are also illustrated. In FIG. 1 , application of the imaging lens 1 to an imaging device is considered, and an imaging device 5 provided at an image plane Sim including an image point Pim of the imaging lens 1 is also illustrated. The imaging device 5 converts an optical image formed by the imaging lens 1 into an electrical signal. For example, a CCD image sensor, a CMOS image sensor, or the like can be used as the imaging device 5 . the

When the imaging lens 1 is applied to an imaging device, it is desirable to provide a cover glass and a low-pass filter, an infrared cut filter, and the like based on the structure of a camera on which the lens is mounted. Fig. 1 illustrates an example in which a parallel plate-shaped optical member PP assumed to be such an element is disposed between the most image-side lens and the imaging device 5 (image plane Sim). the

First, the structure according to the first embodiment of the present invention will be described. The imaging lens according to the first embodiment of the present invention includes a negative first lens L1, a negative second lens L2, a positive third lens L3, a positive fourth lens L4, a negative first lens L4, and a negative first lens L1 arranged sequentially from the object side. Pentalens L5 and positive sixth lens L6. In the example illustrated in FIG. 1 , aperture stop St is disposed between third lens L3 and fourth lens L4 . In FIG. 1 , the aperture stop St does not represent the shape or size of the aperture stop St, but represents the position of the aperture stop St on the optical axis Z. As shown in FIG. Since the aperture stop St is provided between the third lens L3 and the fourth lens L4, it is possible to reduce the size of the entire system. When the aperture stop St is positioned close to the object side, the outer diameter of the first lens L1 can be easily reduced. However, if aperture stop St is too close to the object side, it becomes difficult to separate on-axis rays and off-axis rays from each other at first lens L1 and second lens L2, and it becomes difficult to correct field curvature. When aperture stop St is provided between third lens L3 and fourth lens L4, field curvature can be easily corrected while reducing the lens diameter. the

The imaging lens is composed of at least six lenses, which is a small number of lenses. Therefore, it is possible to reduce the cost of the imaging lens and reduce the overall length of the imaging lens in the direction of the optical axis. Further, since the first lens L1 and the second lens L2 which are two lenses provided on the object side are both negative lenses, it is possible to easily widen the angle of view of the entire lens system. Further, since the two negative lenses are disposed closest to the object side, the negative refractive power can be shared by the two lenses, and light entering at a wide angle of view can be gradually bent. Therefore, distortion can be effectively corrected. Further, there are three positive lenses of the third lens L3, the fourth lens L4, and the sixth lens L6. Therefore, these three lenses can share the converging action performed by one or more positive lenses for forming an image on the image plane and correcting various aberrations. Therefore, correction can be effectively performed. the

When third lens L3 is a positive lens, field curvature can be excellently corrected. When fourth lens L4 is a positive lens and fifth lens L5 is a negative lens, longitudinal chromatic aberration and lateral chromatic aberration can be excellently corrected. When sixth lens L6 is a positive lens, it is possible to reduce the angle at which peripheral rays enter the image forming surface of the imaging lens. Therefore, shading can be suppressed. When fourth lens L4 is a positive lens, fifth lens L5 is a negative lens, and sixth lens L6 is a positive lens, spherical aberration and curvature of field can be excellently corrected. When negative refractive power, negative refractive power, positive refractive power, positive refractive power, negative refractive power, and positive refractive power are sequentially set from the object side, it is possible to obtain a small size with a wide field of view and excellent resolution performance lens system, even if the lens system has a small F-number. the

The imaging lens according to the first embodiment of the present invention satisfies the following conditional formulas (1) and (6):

-0.61<(R8+R9)/(R8-R9)<0.44...(1); and

38.1<vd3+vd5<45.1...(6), where

R8: radius of curvature of the object-side surface of the fourth lens,

R9: radius of curvature of the image side surface of the fourth lens,

vd3: the Abbe number of the material of the third lens with respect to the d-line, and

vd5: the Abbe number of the material of the fifth lens with respect to the d line. the

When the upper and lower limits of conditional formula (1) are satisfied, fourth lens L4 can be made into a biconvex lens, and the refractive power of fourth lens L4 can be easily increased. Therefore, chromatic aberration can be easily corrected. When the lower limit of conditional formula (1) is satisfied, it is possible to easily prevent the radius of curvature of the object-side surface from becoming small, and to easily correct curvature of field and coma aberration. When the upper limit of conditional formula (1) is satisfied, the difference between the absolute value of the radius of curvature of the front surface and the absolute value of the radius of curvature of the rear surface can be easily suppressed, and spherical aberration can be easily corrected. the

If the value is lower than the lower limit of conditional formula (6), one or both of the Abbe number of third lens L3 and the Abbe number of fifth lens L5 will become too small. Longitudinal chromatic aberration and lateral chromatic aberration can be easily corrected. However, the material cost is high, and it becomes difficult to manufacture the lens system at low cost. If the value exceeds the upper limit of conditional formula (6), one or both of the Abbe number of third lens L3 and the Abbe number of fifth lens L5 becomes large, and it is difficult to correct longitudinal chromatic aberration and lateral chromatic aberration Difference. the

Next, the structure of the second embodiment of the present invention will be described. The imaging lens according to the second embodiment of the present invention includes a negative first lens L1, a negative second lens L2, a positive third lens L3, a positive fourth lens L4, a negative first lens L4, and a negative first lens L1 arranged sequentially from the object side. Pentalens L5 and positive sixth lens L6. the

The imaging lens is composed of at least six lenses, which is a small number of lenses. Therefore, it is possible to reduce the cost of the imaging lens and reduce the overall length of the imaging lens in the direction of the optical axis. Further, since the first lens L1 and the second lens L2 which are two lenses provided on the object side are both negative lenses, it is possible to easily widen the angle of view of the entire lens system. Further, since the two negative lenses are disposed closest to the object side, the two lenses can share the refractive power, and can gradually bend light entering at a wide angle of view. Therefore, distortion can be effectively corrected. Further, there are three positive lenses of the third lens L3, the fourth lens L4, and the sixth lens L6. Therefore, these three lenses can share the converging action performed by one or more positive lenses for forming an image on the image plane and correcting various aberrations. Therefore, correction can be effectively performed. the

When third lens L3 is a positive lens, field curvature can be excellently corrected. When fourth lens L4 is a positive lens and fifth lens L5 is a negative lens, longitudinal chromatic aberration and lateral chromatic aberration can be excellently corrected. When sixth lens L6 is a positive lens, it is possible to reduce the angle at which peripheral rays enter the image forming surface of the imaging lens. Therefore, shading can be suppressed. When fourth lens L4 is a positive lens, fifth lens L5 is a negative lens, and sixth lens L6 is a positive lens, spherical aberration and curvature of field can be excellently corrected. When negative refractive power, negative refractive power, positive refractive power, positive refractive power, negative refractive power, and positive refractive power are sequentially set from the object side, it is possible to obtain a small size with a wide field of view and excellent resolution performance lens system, even if the lens system has a small F-number. the

The imaging lens according to the second embodiment of the present invention satisfies the following conditional formulas (1-1) and (12):

-0.11<(R8+R9)/(R8-R9)...(1-1); and

R9/f<-2.9...(12), where

R8: radius of curvature of the object-side surface of the fourth lens,

R9: the radius of curvature of the image-side surface of the fourth lens, and

f: focal length of the whole system. the

When the lower limit of conditional formula (1-1) is satisfied, fourth lens L4 can be made a biconcave lens, and the refractive power of fourth lens L4 can be easily increased. Therefore, chromatic aberration can be easily corrected. When the lower limit of conditional formula (1-1) is satisfied, it is possible to easily prevent the radius of curvature of the object-side surface from becoming small and to easily correct field curvature and coma aberration. the

When the upper limit of conditional formula (12) is satisfied, the absolute value of the radius of curvature of the image-side surface of fourth lens L4 can be easily prevented from becoming too small, and the edge portion of fourth lens L4 can be easily increased. Therefore, the fourth lens L4 can be easily handled, and the cost can be easily reduced. the

Next, the structure of a third embodiment of the present invention will be described. The imaging lens according to the third embodiment of the present invention includes a negative first lens L1, a negative second lens L2, a positive third lens L3, a positive fourth lens L4, a negative first lens L4, and a negative first lens L1 arranged sequentially from the object side. Penta lens L5 and positive sixth lens L6. the

The imaging lens is composed of at least six lenses, which is a small number of lenses. Therefore, it is possible to reduce the cost of the imaging lens and reduce the overall length of the imaging lens in the direction of the optical axis. Further, since the first lens L1 and the second lens L2 which are two lenses provided on the object side are both negative lenses, it is possible to easily widen the angle of view of the entire lens system. Further, since the two negative lenses are disposed closest to the object side, the two lenses can share the refractive power, and can gradually bend light entering at a wide angle of view. Therefore, distortion can be effectively corrected. Further, there are three positive lenses of the third lens L3, the fourth lens L4, and the sixth lens L6. Therefore, these three lenses can share the converging action performed by one or more positive lenses for forming an image on the image plane and correcting various aberrations. Therefore, correction can be effectively performed. the

When third lens L3 is a positive lens, field curvature can be excellently corrected. When fourth lens L4 is a positive lens and fifth lens L5 is a negative lens, longitudinal chromatic aberration and lateral chromatic aberration can be excellently corrected. When sixth lens L6 is a positive lens, it is possible to reduce the angle at which peripheral rays enter the image forming surface of the imaging lens. Therefore, shading can be suppressed. When fourth lens L4 is a positive lens, fifth lens L5 is a negative lens, and sixth lens L6 is a positive lens, spherical aberration and curvature of field can be excellently corrected. When negative refractive power, negative refractive power, positive refractive power, positive refractive power, negative refractive power, and positive refractive power are sequentially set from the object side, it is possible to obtain a small size with a wide field of view and excellent resolution performance lens system, even if the lens system has a small F-number. the

The imaging lens according to the third embodiment of the present invention satisfies the following conditional formulas (1-2) and (4):

-0.075<(R8+R9)/(R8-R9)<0.11...(1-2); and

-1.04<(R10+R11)/(R10-R11)<-0.34...(4), where

R8: radius of curvature of the object-side surface of the fourth lens,

R9: radius of curvature of the image side surface of the fourth lens,

R10: the radius of curvature of the object-side surface of the fifth lens, and

R11: radius of curvature of the image-side surface of the fifth lens. the

When the upper and lower limits of conditional formula (1-2) are satisfied, fourth lens L4 can be made into a biconvex lens, and the refractive power of fourth lens L4 can be easily increased. Therefore, chromatic aberration can be easily corrected. When the lower limit of conditional formula (1-2) is satisfied, it is possible to easily prevent the radius of curvature of the object-side surface from becoming small, and to easily correct field curvature and coma aberration. When the upper limit of conditional formula (1-2) is satisfied, the difference between the absolute value of the radius of curvature of the front surface and the absolute value of the radius of curvature of the rear surface can be easily suppressed, and spherical aberration can be easily corrected. the

When the lower limit of conditional formula (4) is satisfied, it is possible to easily prevent the refractive power of fifth lens L5 from being weakened, and to easily correct chromatic aberration. When the upper limit of conditional formula (4) is satisfied, it is possible to easily prevent the radius of curvature of the object-side surface of fifth lens L5 from becoming large, and to easily correct chromatic aberration. Or it is possible to easily prevent the radius of curvature of the image-side surface of fifth lens L5 from becoming too small, and to easily widen the angle of view. Alternatively, curvature of field and coma aberration can be easily corrected. the

Next, the structure of a fourth embodiment of the present invention will be described. The imaging lens according to the fourth embodiment of the present invention includes a negative first lens L1, a negative second lens L2, a positive third lens L3, a positive fourth lens L4, a negative first lens L4, and a negative first lens L1 sequentially arranged from the object side. Pentalens L5 and positive sixth lens L6. the

The imaging lens is composed of at least six lenses, which is a small number of lenses. Therefore, it is possible to reduce the cost of the imaging lens and reduce the overall length of the imaging lens in the direction of the optical axis. Further, since the first lens L1 and the second lens L2 which are two lenses provided on the object side are both negative lenses, it is possible to easily widen the angle of view of the entire lens system. Further, since the two negative lenses are disposed closest to the object side, the two lenses can share the refractive power, and can gradually bend light entering at a wide angle of view. Therefore, distortion can be effectively corrected. Further, there are three positive lenses of the third lens L3, the fourth lens L4, and the sixth lens L6. Therefore, these three lenses can share the converging action performed by one or more positive lenses for forming an image on the image plane and correcting various aberrations. Therefore, correction can be effectively performed. the

When third lens L3 is a positive lens, field curvature can be excellently corrected. When fourth lens L4 is a positive lens and fifth lens L5 is a negative lens, longitudinal chromatic aberration and lateral chromatic aberration can be excellently corrected. When sixth lens L6 is a positive lens, it is possible to reduce the angle at which peripheral rays enter the image forming surface of the imaging lens. Therefore, shading can be suppressed. When fourth lens L4 is a positive lens, fifth lens L5 is a negative lens, and sixth lens L6 is a positive lens, spherical aberration and curvature of field can be excellently corrected. When negative refractive power, negative refractive power, positive refractive power, positive refractive power, negative refractive power, and positive refractive power are sequentially set from the object side, it is possible to obtain a small size with a wide field of view and excellent resolution performance lens system, even if the lens system has a small F-number. the

Further, in the imaging lens according to the fourth embodiment, the object-side surface of third lens L3 is concave. When the object-side surface of third lens L3 is concave, the angle of view can be easily widened, and paraxial rays and peripheral rays are easily separated from each other at first lens L1 and second lens L2 . the

The imaging lens according to the fourth embodiment of the present invention satisfies the following conditional formulas (1-3) and (4-1):

(R8+R9)/(R8-R9)<0.17...(1-3); and

(R10+R11)/(R10-R11)<-0.35...(4-1), where

R8: radius of curvature of the object-side surface of the fourth lens,

R9: radius of curvature of the image side surface of the fourth lens,

R10: the radius of curvature of the object-side surface of the fifth lens, and

R11: radius of curvature of the image-side surface of the fifth lens. the

When the upper limit of conditional formula (1-3) is satisfied, fourth lens L4 can be made into a biconvex lens, and it is easy to increase the refractive power of fourth lens L4. Therefore, chromatic aberration can be easily corrected. When the upper limit of conditional formula (1-3) is satisfied, the difference between the absolute value of the radius of curvature of the front surface and the absolute value of the radius of curvature of the rear surface can be easily suppressed, and spherical aberration can be easily corrected. the

When the upper limit of conditional formula (4-1) is satisfied, it is possible to easily prevent the radius of curvature of the object-side surface of fifth lens L5 from becoming large, and to easily correct chromatic aberration. Alternatively, it is possible to easily prevent the radius of curvature of the image-side surface of fifth lens L5 from becoming too small, and to easily widen the angle of view. Alternatively, curvature of field and coma aberration can be easily corrected. the

Next, the structure of a fifth embodiment of the present invention will be described. The imaging lens according to the fifth embodiment of the present invention includes a negative first lens L1, a negative second lens L2, a positive third lens L3, a positive fourth lens L4, a negative first lens L4, and a negative first lens L1 arranged sequentially from the object side. Pentalens L5 and positive sixth lens L6. the

The imaging lens is composed of at least six lenses, which is a small number of lenses. Therefore, it is possible to reduce the cost of the imaging lens and reduce the overall length of the imaging lens in the direction of the optical axis. Further, since the first lens L1 and the second lens L2 which are two lenses provided on the object side are both negative lenses, it is possible to easily widen the angle of view of the entire lens system. Further, since the two negative lenses are disposed closest to the object side, the two lenses can share the refractive power, and can gradually bend light entering at a wide angle of view. Therefore, distortion can be effectively corrected. Further, there are three positive lenses of the third lens L3, the fourth lens L4, and the sixth lens L6. Therefore, these three lenses can share the converging action performed by one or more positive lenses for forming an image on the image plane and correcting various aberrations. Therefore, correction can be effectively performed. the

When third lens L3 is a positive lens, field curvature can be excellently corrected. When fourth lens L4 is a positive lens and fifth lens L5 is a negative lens, longitudinal chromatic aberration and lateral chromatic aberration can be excellently corrected. When sixth lens L6 is a positive lens, it is possible to reduce the angle at which peripheral rays enter the image forming surface of the imaging lens. Therefore, shading can be suppressed. When the fourth lens L4 is a positive lens, the fifth lens L5 is a negative lens, and the sixth lens L6 is a positive lens, it is possible to excellently correct spherical aberration and curvature of field. When negative refractive power, negative refractive power, positive refractive power, positive refractive power, negative refractive power, and positive refractive power are sequentially set from the object side, it is possible to obtain a small size with a wide field of view and excellent resolution performance lens system, even if the lens system has a small F-number. the

Further, in the imaging lens according to the fifth embodiment, the object-side surface of third lens L3 is concave, fourth lens L4 is a biconvex lens, and fifth lens L5 is a biconcave lens. When the object-side surface of third lens L3 is concave, the angle of view can be easily widened, and paraxial rays and peripheral rays are easily separated from each other at first lens L1 and second lens L2 . When fourth lens L4 is a biconvex lens, it is possible to easily increase the refractive power of fourth lens L4, and to easily correct longitudinal and lateral chromatic aberrations between fourth lens L4 and fifth lens L5. When fifth lens L5 is a biconcave lens, it is possible to easily increase the refractive power of fifth lens L5, and to easily correct longitudinal and lateral chromatic aberrations between fourth lens L4 and fifth lens L5. the

The imaging lens according to the fifth embodiment of the present invention satisfies the following conditional formulas (1-3) and (4-1):

(R8+R9)/(R8-R9)<0.17...(1-3); and

(R10+R11)/(R10-R11)<-0.35...(4-1), where

R8: radius of curvature of the object-side surface of the fourth lens,

R9: radius of curvature of the image side surface of the fourth lens,

R10: the radius of curvature of the object-side surface of the fifth lens, and

R11: radius of curvature of the image-side surface of the fifth lens. the

When the upper limit of conditional formula (1-3) is satisfied, fourth lens L4 can be made into a biconvex lens, and it is easy to increase the refractive power of fourth lens L4. Therefore, chromatic aberration can be easily corrected. When the upper limit of conditional formula (1-3) is satisfied, the difference between the absolute value of the radius of curvature of the front surface and the absolute value of the radius of curvature of the rear surface can be easily suppressed, and spherical aberration can be easily corrected. the

When the upper limit of conditional formula (4-1) is satisfied, it is possible to easily prevent the radius of curvature of the object-side surface of fifth lens L5 from becoming large, and to easily correct chromatic aberration. Alternatively, it is possible to easily prevent the radius of curvature of the image-side surface of fifth lens L5 from becoming too small, and to easily widen the angle of view. Alternatively, curvature of field and coma aberration can be easily corrected. the

Next, structures to be ideally included in the imaging lenses according to the first to fifth embodiments will be given, and actions and effects of the structures will be described. As an ideal mode, the imaging lens may include one of the following structures, or a combination of any two or more of the following structures. the

It is hoped that the following conditional formula (9) is satisfied:

2<f3/f<12...(9), where

f3: the focal length of the third lens L3, and

f: focal length of the whole system. the

When the lower limit of conditional formula (9) is satisfied, it is possible to prevent the refractive power of third lens L3 from becoming too strong, and easily secure a back focus. When the upper limit of conditional formula (9) is satisfied, the refractive power of third lens L3 can be prevented from becoming too weak, and field curvature and lateral chromatic aberration can be easily corrected. the

It is hoped that the following conditional formula (19) is satisfied:

1<(D4+D5)/f<6...(19), where

D4: The air gap on the optical axis between the second lens L2 and the third lens L3,

D5: the central thickness of the third lens L3, and

f: focal length of the whole system. the

When the lower limit of the conditional formula (19) is satisfied, the distance between the second lens L2 and the third lens L3 and the center thickness of the third lens L3 can be prevented from becoming too small, while the distance between the first lens L1 and the second lens L2 It is easy to separate the on-axis and off-axis rays from each other. Further, curvature of field, distortion, and coma can be easily corrected. When the upper limit of conditional formula (19) is satisfied, the distance between second lens L2 and third lens L3 and the center thickness of third lens L3 can be prevented from becoming too large, and the entire lens can be easily downsized. the

It is hoped that the following conditional formula (20) is satisfied:

-1<f/R5<1...(20), where

f: the focal length of the entire system, and

R5: radius of curvature of the object-side surface of third lens L3. the

If the value is lower than the lower limit of conditional formula (20), the object-side surface of third lens L3 is a concave surface facing the object side, and the radius of curvature of the object-side surface of third lens L3 becomes too small. Therefore, the refractive power of third lens L3 becomes weak, and correction of lateral chromatic aberration becomes difficult. If the value exceeds the upper limit of conditional formula (20), the object-side surface of third lens L3 is convex toward the object side, and the radius of curvature of the object-side surface of third lens L3 becomes too small. Therefore, the refractive power of third lens L3 becomes too strong, and lateral chromatic aberration can be excellently corrected. However, it becomes difficult to correct curvature of field, and to secure a back focus. the

It is hoped that the following conditional formula (21) is satisfied:

-3<f/R3<3...(21), where

f: the focal length of the entire system, and

R3: radius of curvature of the object-side surface of second lens L2. the

If the value is lower than the lower limit of conditional formula (21), the object-side surface of second lens L2 is a concave surface facing the object side, and the radius of curvature of the object-side surface of second lens L2 becomes too small. Therefore, the light rays are sharply bent at this surface. Therefore, correction of distortion becomes difficult. If the value exceeds the upper limit of conditional formula (21), the object-side surface of second lens L2 is convex, and the radius of curvature of the object-side surface of second lens L2 becomes too small. Therefore, the refractive power of second lens L2 becomes weak, and it becomes difficult to widen the angle of field, or the size of the lens system becomes large. the

It is hoped that the following conditional formula (22) is satisfied:

-30<f23/f<-3...(22), where

f23: the combined focal length of the second lens L2 and the third lens L3, and

f: focal length of the whole system. the

When the lower limit of conditional formula (22) is satisfied, it is possible to prevent the refractive power of second lens L2 from becoming too weak, and to easily widen the angle of view. When the upper limit of conditional formula (22) is satisfied, the refractive power of third lens L3 can be prevented from becoming weak and lateral chromatic aberration can be easily corrected, or the refractive power of second lens L2 can be prevented from becoming too strong and distortion can be easily corrected . the

It is hoped that the following conditional formula (23) is satisfied:

2<f45/f<25...(23), where

f45: the combined focal length of the fourth lens L4 and the fifth lens L5, and

f: focal length of the whole system. the

If the value is lower than the lower limit of conditional formula (23), the combined focal length of fourth lens L4 and fifth lens L5 becomes too small, and it becomes difficult to secure a back focus. If the value exceeds the upper limit of conditional formula (23), the combined focal length of fourth lens L4 and fifth lens L5 becomes too large, and it becomes difficult to excellently correct longitudinal and lateral chromatic aberrations. the

It is hoped that the following conditional formula (24) is satisfied:

9<L/f<20...(24), where

L: the length from the object-side surface of the first lens to the image plane on the optical axis (the back focus part is the distance in air), and

f: focal length of the whole system. the

If the value exceeds the upper limit of conditional formula (24), the angle of field can be easily widened, but the size of the lens system becomes large. If the value is lower than the lower limit of conditional formula (24), the lens system can be downsized, but it becomes difficult to widen the angle of field. the

It is hoped that the following conditional formula (25) is satisfied:

1<Bf/f<3...(25), where

Bf - the length (distance in air) from the image side surface of the lens closest to the image side to the image plane on the optical axis, and

f: focal length of the whole system. the

When the upper limit of conditional formula (25) is satisfied, the lens system can be easily reduced in size. When the lower limit of conditional formula (25) is satisfied, it is possible to easily secure the back focus, and to easily provide various filters, cover glass, and the like between the lens and the sensor. the

It is hoped that the following conditional formula (26) is satisfied:

1.1≤(R1+R2)/(R1-R2)≤3.0...(26), where

R1: the radius of curvature of the object-side surface of the first lens L1, and

R2: radius of curvature of the image-side surface of first lens L1. the

When conditional formula (26) is satisfied, first lens L1 can be made as a meniscus lens having a convex surface facing the object side. When the first lens L1 is a meniscus lens having a convex surface facing the object side, it is possible to exceed 180. The wide field of view receives light and easily corrects distortion. When the upper limit of conditional formula (26) is satisfied, the radius of curvature of the object-side surface of first lens L1 and the radius of curvature of the image-side surface of first lens L1 can be prevented from becoming too close to each other. Further, the refractive power of first lens L1 can be easily increased. Therefore, it is possible to easily widen the angle of view. When the lower limit of conditional formula (26) is satisfied, the radius of curvature of the object-side surface of first lens L1 can be easily reduced, and distortion can be easily corrected. the

Regarding each of the foregoing conditional formulas, it is desirable to satisfy a conditional formula in which the upper limit is further increased, or a conditional formula in which the lower limit or the upper limit is modified, as will be described below. As an ideal mode, in combination, a conditional formula employing a modified lower limit and a modified upper limit as will be described next may be satisfied. Next, an ideal modification example of the conditional formula as an example will be described. However, modified examples of conditional formulas are not limited to the examples indicated by the following expressions. The described modification values may be used in combination. the

It is desirable that the upper limit of (R8+R9)/(R8-R9) defined by the conditional formula (1), (1-1), (1-2) or (1-3) is 0.44. Therefore, spherical aberration can be easily corrected. It is desirable that the upper limit of conditional formula (1) is 0.43 to more easily correct spherical aberration. More desirable, the upper limit is 0.25, and 0.17 is even more desirable, and 0.16 is still more desirable. Further, it is more desirable that the upper limit is 0.12, and 0.11 is even more desirable. the

Desirably, the lower limit of (R8+R9)/(R8-R9) is -0.61. Thus, curvature of field and coma aberration can be easily corrected. It is desirable that the lower limit of conditional formula (1) is -0.55 to more easily correct field curvature and coma aberration, -0.19 is more desirable, -0.18 is even more desirable, and -0.11 is still more desirable. Further, it is desirable that the lower limit is -0.10, -0.075 is more desirable, and -0.06 is most desirable. the

Therefore, for example, it is desirable that the following condition formulas (1-4) to (1-7) be satisfied:

-0.10<(R8+R9)/(R8-R9)<0.25...(1-4);

-0.06<(R8+R9)/(R8-R9)<0.2...(1-5);

-0.10<(R8+R9)/(R8-R9)<0.16...(1-6); or

-0.06<(R8+R9)/(R8-R9)<0.12...(1-7). the

Desirably, the upper limit of (R10+R11)/(R10-R11) defined by conditional formula (4) or (4-1) is -0.35. Thus, chromatic aberration, curvature of field, and coma aberration can be easily corrected. It is desirable that the upper limit of (R10+R11)/(R10-R11) is -0.34 to more easily correct chromatic aberration, curvature of field, and coma aberration. More desirable, the upper bound is -0.33, -0.40 is even more desirable, and -0.50 is still more desirable. Further, it is more desirable that the upper limit is -0.52. 

It is desirable that the lower limit of the conditional formula (R10+R11)/(R10-R11) is -2.68. Thus, the refractive power of fifth lens L5 can be easily increased, and chromatic aberration can be easily corrected. It is desirable that the lower limit of conditional formula (4) is -2.0 to more easily correct chromatic aberration, -1.5 is even more desirable, and -1.3 is still more desirable. Further, it is more desirable that the lower limit is -1.2, and -1.04 is even more desirable. the

Therefore, for example, it is desirable that the following conditional formulas (4-2) to (4-5) are satisfied:

-2.68<(R10+R11)/(R10-R11)<-0.34...(4-2)

-1.5<(R10+R11)/(R10-R11)<-0.33...(4-3);

-1.3<(R10+R11)/(R10-R11)<-0.40...(4-4); or

-1.04<(R10+R11)/(R10-R11)<-0.52...(4-5). the

It is desirable that the upper limit of conditional formula (6) is 45.0. Thus, longitudinal chromatic aberration and lateral chromatic aberration can be easily corrected. It is desirable that the upper limit of conditional formula (6) is 44.8 to more easily correct longitudinal chromatic aberration and lateral chromatic aberration, and 44.5 is even more desirable. the

It is desirable that the lower limit of conditional formula (6) is 40.0. Thus, the lens system can be easily manufactured at low cost. It is desirable that the lower limit of conditional formula (6) is 41.0 to further reduce the cost of the lens system, and 41.5 is more desirable, 42.0 is even more desirable, and 42.2 is still more desirable. the

Therefore, for example, it is desirable that the following condition formulas (6-1) to (6-3) are satisfied:

41.0<vd3+vd5<45.1...(6-1);

42.0<vd3+vd5<44.8...(6-2); or

42.2<vd3+vd5<44.5...(6-3). the

It is desirable that the upper limit of conditional formula (9) is 13. Thus, curvature of field and lateral chromatic aberration can be more easily corrected. It is more desirable that the upper limit of conditional formula (9) is 12 in order to more easily correct curvature of field and lateral chromatic aberration. Even more desirable is that the upper limit is 10. the

It is desirable that the lower limit of conditional formula (9) is 4. Therefore, the back focus can be secured more easily. It is more desirable that the lower limit of conditional formula (9) is 5 to more easily secure the back focus. It is even more desirable that the lower limit is 5.5. the

Therefore, for example, it is desirable that the following condition formula (9-1), (9-2) or (9-3) be satisfied:

4<f3/f<13...(9-1);

5<f3/f<12...(9-2); or

5.5<f3/f<10...(9-3). the

It is desirable that the upper limit of conditional formula (12) is -2.95. Thus, chromatic aberration can be corrected more easily. It is desirable that the upper limit of conditional formula (12) is -2.98 to more easily correct chromatic aberration, and -3.0 is even more desirable. the

It is desirable to set the lower limit of conditional formula (12). In this case, it is desirable that the lower limit is -6.2. Thus, it is possible to prevent the absolute value of the radius of curvature of the image-side surface of fourth lens L4 from becoming too small, and to easily provide fourth lens L4 with a large edge portion. Therefore, it becomes possible to easily process the fourth lens L4, and it becomes easy to suppress the cost. It is desirable that the lower limit of conditional formula (12) is -6.1 to more easily process the fourth lens L4, and to further suppress the cost, -5.0 is more desirable, -4.4 is even more desirable, and -4.3 is still more desirable of. Further, it is desirable that the lower limit is -4.2. the

Therefore, for example, it is desirable that the following condition formulas (12-1) to (12-4) be satisfied:

R9/f<-2.95...(12-1);

-6.1<R9/f<-2.95...(12-2);

-5.0<R9/f<-2.98...(12-3); or

-4.3<R9/f<-3.0...(12-4). the

It is desirable that the lower limit of conditional formula (19) is 1.4. Thus, curvature of field, distortion and coma can be easily corrected. It is desirable that the lower limit of conditional formula (19) is 1.7 to more easily correct curvature of field, distortion and coma. It is even more desirable that the lower limit is 1.9. the

It is desirable that the upper limit of conditional formula (19) is 5.5. Thus, the size of the system can be reduced more easily. It is desirable that the upper limit of conditional formula (19) is 5.0 for easier downsizing, and 4.4 is more desirable. the

Therefore, for example, it is desirable that the following conditional formulas (19-1), (19-2) or (19-3) be satisfied:

1.4<(D4+D5)/f<5.5...(19-1);

1.7<(D4+D5)/f<5.0...(19-2); or

1.9<(D4+D5)/f<4.4...(19-3). the

It is desirable that the lower limit of conditional formula (20) is -0.9. Thus, lateral chromatic aberration can be more easily corrected. It is desirable that the lower limit of conditional formula (20) is -0.5 to more easily correct lateral chromatic aberration. Even more desirable is that the lower bound is -0.2. the

It is desirable that the upper limit of conditional formula (20) is 0.9. Therefore, curvature of field can be corrected more easily. It is desirable that the upper limit of conditional formula (20) is 0.5 to more easily correct curvature of field, and 0.2 is more desirable. the

Therefore, for example, it is desirable that the following conditional formulas (20-1), (20-2) or (20-3) be satisfied:

-0.9<f/R5<0.9...(20-1);

-0.5<f/R5<0.5...(20-2); or

-0.2<f/R5<0.2...(20-3). the

It is desirable that the lower limit of conditional formula (21) is -2.5. Thus, distortion can be easily corrected. It is desirable that the lower limit of conditional formula (21) is -2.0 to more easily correct distortion. More desirably, the lower limit is -1.5. the

It is desirable that the upper limit of conditional formula (21) is 2.0. Thus, it is easier to widen the angle of view, and it is easier to reduce the size of the system. It is desirable that the upper limit of conditional formula (21) is 1.5 to more easily widen the angle of field and reduce the size of the system, and 1.0 is more desirable. the

Therefore, for example, it is desirable that the following condition formula (21-1), (21-2) or (21-3) be satisfied:

-2.5<f/R3<2.0...(21-1);

-2.0<f/R3<1.5...(21-2); or

-1.5<f/R3<1.0...(21-3). the

It is desirable that the lower limit of conditional formula (22) is -25. Therefore, it is possible to more easily widen the angle of view. It is desirable that the lower limit of conditional formula (22) is -20 to more easily widen the angle of view. More desirably, the lower limit is -19.5. the

It is desirable that the upper limit of conditional formula (22) is -4. Thus, lateral chromatic aberration or distortion can be corrected more easily. It is desirable that the upper limit of conditional formula (22) is -5 to more easily correct lateral chromatic aberration or distortion, and -5.5 is more desirable. the

Therefore, for example, it is desirable that the following conditional formulas (22-1), (22-2) or (22-3) be satisfied:

-25<f23/f<-4...(22-1);

-20<f23/f<-5...(22-2); or

-19.5<f23/f<-5.5...(22-3). the

It is desirable that the lower limit of conditional formula (23) is 3. Therefore, the back focus can be easily secured. It is desirable that the lower limit of conditional formula (23) is 4 to more easily secure the back focus. More desirably, the lower limit is 4.1. the

It is desirable that the upper limit of conditional formula (23) is 22. Thus, longitudinal chromatic aberration and lateral chromatic aberration can be more easily corrected. It is desirable that the upper limit of conditional formula (23) is 20 to more easily correct longitudinal chromatic aberration and lateral chromatic aberration, and 18 is more desirable. the

Therefore, for example, it is desirable that the following condition formula (23-1), (23-2) or (23-3) be satisfied:

3<f45/f<22...(23-1);

4<f45/f<20...(23-2); or

4.1<f45/f<18...(23-3). the

It is desirable that the upper limit of conditional formula (24) is 19.8. When the upper limit of conditional formula (24) is 19.8, it is possible to more easily reduce the size of the lens system. Further, it is more desirable that the upper limit of conditional formula (24) is 19.3. Even more desirable is that the upper limit is 19.0. the

It is desirable that the lower limit of conditional formula (24) is 9.5. When the lower limit of conditional formula (24) is 9.5, it is possible to more easily widen the angle of view. It is desirable that the lower limit of conditional formula (24) is 10. Even more desirable is that the lower limit is 10.2. the

Therefore, for example, it is desirable that the following conditional formulas (24-1), (24-2) or (24-3) be satisfied:

9.5<L/f<19.8...(24-1);

10<L/f<19.3...(24-2); or

10.2<L/f<19.0...(24-3). the

It is desirable that the upper limit of conditional formula (25) is 2.95. When the upper limit of conditional formula (25) is 2.95, it is possible to more easily reduce the size of the system. It is more desirable that the upper limit of conditional formula (25) is 2.9 to reduce the size of the system. It is even more desirable that the upper limit is 2.85, and 2.3 is yet more desirable. the

It is desirable that the lower limit of conditional formula (25) is 1.5. When the lower limit of conditional formula (25) is 1.5, the back focus can be secured more easily. More desirably, the lower limit of conditional formula (25) is 1.8. Even more desirable is that the lower limit is 1.85. the

Therefore, for example, it is desirable that the following conditional formula (25-1) or (25-2) be satisfied:

1.5<Bf/f<2.95...(25-1); or

1.85<Bf/f<2.85...(25-2). the

It is desirable that the upper limit of conditional formula (26) is 2.5. Therefore, it is possible to more easily widen the angle of view. It is desirable that the upper limit of conditional formula (26) is 2.0 to more easily widen the angle of view. Even more desirable is that the upper limit is 1.9. 

It is desirable that the lower limit of conditional formula (26) is 1.2. Thus, distortion can be corrected more easily. Further, it is desirable that the lower limit of conditional formula (26) is 1.3. Even more desirable is that the lower limit is 1.4. Still more desirable is a lower bound of 1.5. the

Therefore, for example, it is desirable that the following conditional formulas (26-1), (26-2) or (26-3) be satisfied:

1.2≤(R1+R2)/(R1-R2)≤2.5...(26-1);

1.3≤(R1+R2)/(R1-R2)≤2.0...(26-2); or

1.5≤(R1+R2)/(R1-R2)<1.9...(26-3). the

It is desirable that an aperture stop is provided between third lens L3 and fourth lens L4. When the aperture stop is disposed between third lens L3 and fourth lens L4, it is possible to reduce the size of the entire system. If the aperture stop is positioned close to the object side, the outer diameter of first lens L1 can be easily reduced. However, if the aperture stop is too close to the object side, it becomes difficult to separate on-axis rays and off-axis rays from each other at first lens L1 and second lens L2. Further, it becomes difficult to correct curvature of field. When the aperture stop is provided between third lens L3 and fourth lens L4, field curvature can be easily corrected while reducing the lens diameter. the

It is desirable that the materials of the first lens L1, the second lens L2, the fourth lens L4, and the sixth lens L6 have an Abbe number of 40 or more with respect to the d-line. Thus, generation of chromatic aberration can be suppressed, and excellent resolution performance can be achieved. More desirably, the Abbe number is greater than or equal to 47. the

It is desirable that the material of second lens L2 has an Abbe number with respect to the d-line of 50 or more. Thus, the occurrence of chromatic aberration can be further suppressed, and excellent resolution performance can be achieved. More desirably, the Abbe number is greater than or equal to 52. the

It is desirable that the material of sixth lens L6 has an Abbe number of 50 or more with respect to the d-line. Thus, the occurrence of chromatic aberration can be further suppressed, and excellent resolution performance can be achieved. More desirably, the Abbe number is greater than or equal to 52. the

It is desirable that the Abbe number of the material of third lens L3 with respect to the d-line is 40 or less. Thus, lateral chromatic aberration can be excellently corrected. More desirably, the Abbe number is 30 or less. Even more desirably, the Abbe number is 28 or less. It is still more desirable that the Abbe number is less than or equal to 25. the

It is desirable that the material of fifth lens L5 has an Abbe number of 40 or less with respect to the d-line. Thus, lateral chromatic aberration can be excellently corrected. More desirably, the Abbe number is 30 or less. Even more desirably, the Abbe number is 28 or less. Still more desirably, the Abbe number is 25 or less. More desirably, the Abbe number is 20 or less. the

When the Abbe number of the material of the first lens L1 with respect to the d-line is vd1, and the Abbe number of the material of the second lens L2 with respect to the d-line is vd2, it is desirable that vd1/vd2 is greater than or equal to 0.7. Thus, generation of chromatic aberration can be suppressed, and excellent resolution performance can be achieved. Further, it is more desirable that vd1/vd2 is greater than or equal to 0.8. It is desirable that νd1/νd2 is less than or equal to 1.2 in order to balance the Abbe number of first lens L1 and the Abbe number of second lens L2 and suppress the generation of chromatic aberration. the

When the Abbe number of the material of the second lens L2 with respect to the d-line is νd2, and the Abbe number of the material of the third lens L3 with respect to the d-line is νd3, it is desirable that νd2/νd3 is greater than or equal to 2.0. Thus, longitudinal chromatic aberration and lateral chromatic aberration can be excellently corrected. the

When the Abbe number of the material of the first lens L1 with respect to the d-line is νd1, and the Abbe number of the material of the third lens L3 with respect to the d-line is νd3, it is desirable that νd1/νd3 is greater than or equal to 1.4. Thus, longitudinal chromatic aberration and lateral chromatic aberration can be easily corrected in an excellent manner. Further, it is more desirable that vd1/vd3 is greater than or equal to 1.5 in order to more excellently correct longitudinal chromatic aberration and lateral chromatic aberration. the

When the Abbe number of the material of the first lens L1 with respect to the d-line is νd1, and the Abbe number of the material of the third lens L3 with respect to the d-line is νd3, it is desirable that νd1/νd3 is less than or equal to 2.5. Thus, the Abbe number of third lens L3 can be prevented from becoming too small, and the cost of the material of third lens L3 can be easily reduced, or the Abbe number of first lens L1 can be prevented from becoming too large. Therefore, the refractive power of first lens L1 can be easily increased by increasing the refractive index of first lens L1. Therefore, it is possible to easily reduce the size of the lens system and to easily correct distortion. the

It is desirable that the material of first lens L1 has a refractive index of less than or equal to 1.90 with respect to the d-line. Thus, the cost of the material of the first lens L1 can be easily reduced. Further, when a material having a low refractive index is used, a material having a large Abbe's number becomes selectable. Therefore, correction of chromatic aberration becomes easy. Further, it becomes possible to easily realize excellent resolution performance. Further, it is more desirable that the refractive index is less than or equal to 1.85 for more excellent correction of chromatic aberration. the

It is desirable that the material of first lens L1 has a refractive index with respect to d-line higher than or equal to 1.60. Thus, it is possible to easily increase the refractive power of first lens L1 and to easily widen the angle of view. Further, it becomes possible to easily correct distortion. Further, it is more desirable that the refractive index is higher than or equal to 1.65 to easily widen the angle of view and to easily correct distortion. Even more desirable is that the refractive index is higher than or equal to 1.70. the

It is desirable that the refractive index of the material of second lens L2 with respect to the d-line is less than or equal to 1.70. Thus, the cost of the material of the second lens L2 can be reduced. If the material has a high refractive index, the Abbe number becomes small. Therefore, chromatic aberration increases, and it becomes difficult to achieve excellent resolution performance. More desirably, the refractive index is less than or equal to 1.65 to reduce the cost of the material of the second lens L2. Even more desirable is that the refractive index is less than or equal to 1.60. the

It is desirable that the material of second lens L2 has a refractive index with respect to the d-line higher than or equal to 1.50. Thus, the refractive power of second lens L2 can be easily increased, and distortion can be easily corrected. Further, since the refractive power of second lens L2 can be easily increased, the size of the lens system can be easily reduced. the

It is desirable that the refractive index of the material of third lens L3 with respect to the d-line is less than or equal to 1.75. Thus, the cost of the material of third lens L3 can be reduced. It is more desirable that the refractive index is less than or equal to 1.70 to reduce the cost of the material of third lens L3. Even more desirably, the refractive index is less than or equal to 1.68. Still more desirable is a refractive index less than or equal to 1.65. the

It is desirable that the material of third lens L3 has a refractive index with respect to the d-line higher than or equal to 1.50. Thus, the refractive power of third lens L3 can be easily increased by increasing the refractive index of the material of third lens L3, and lateral chromatic aberration and field curvature can be easily corrected. More desirably, the refractive index is higher than or equal to 1.55 to increase the refractive index of third lens L3. More desirably, the refractive index is higher than or equal to 1.60. the

It is desirable that the material of fourth lens L4 has a refractive index of less than or equal to 1.80 with respect to the d-line. Thus, the cost of the material of fourth lens L4 can be reduced. Further, since a material having a large Abbe number can be easily selected, chromatic aberration can be easily corrected, and excellent resolution performance can be achieved. the

It is desirable that the material of fourth lens L4 has a refractive index with respect to the d-line higher than or equal to 1.50. Thus, the refractive power of fourth lens L4 can be easily increased by increasing the refractive index of the material of fourth lens L4. Since the refractive power of fourth lens L4 increases, spherical aberration at fourth lens L4 can be easily corrected. Further, since light rays can be sharply bent at fourth lens L4, the angle at which peripheral light rays enter the imaging device can be easily suppressed. Therefore, shadowing can be easily suppressed. the

It is desirable that the refractive index of the material of fifth lens L5 with respect to the d-line is higher than or equal to 1.50. Thus, the refractive power of fifth lens L5 can be easily increased by increasing the refractive index of the material of fifth lens L5. Further, since a material having a large Abbe number can be easily selected, chromatic aberration can be easily corrected, and excellent resolution performance can be achieved. More desirably, the refractive index is higher than or equal to 1.55 to increase the refractive index of the material of fifth lens L5. It is even more desirable that the refractive index be higher than or equal to 1.60. It is still more desirable that the refractive index be higher than or equal to 1.8. More desirably, the refractive index is higher than or equal to 1.9. the

It is desirable that the refractive index of the material of sixth lens L6 with respect to the d-line is higher than or equal to 1.50. Thus, the refractive power of sixth lens L6 can be easily increased by increasing the refractive index of the material of sixth lens L6. Therefore, it is possible to easily correct spherical aberration and to easily suppress the angle at which light rays enter the imaging device. Therefore, shading can be suppressed easily. It is desirable that the refractive index of the material of sixth lens L6 with respect to the d-line is less than or equal to 1.70. Thus, a material having a large Abbe's number can be easily selected. Therefore, it becomes possible to easily correct chromatic aberration, and to easily realize excellent resolution performance. It is desirable that the material of sixth lens L6 has a refractive index with respect to the d-line of 1.60 or less in order to correct chromatic aberration. the

It is desirable that the object-side surface of second lens L2 is aspherical. Thus, the size of the lens system can be easily reduced, and the angle of field can be easily widened, or excellent correction of curvature of field and distortion becomes easy. It is desirable that the object-side surface of second lens L2 has a shape having positive refractive power both at the center and at the edge of the effective diameter, and when the positive refractive power at the center and the positive refractive power at the edge of the effective diameter are mutually In comparison, the positive refractive power at the edges of the effective diameter is weaker than that at the center. When the object-side surface of second lens L2 has such a shape, it is possible to reduce the size of the lens system. At the same time, the angle of view can be easily widened. the

Here, the term "effective diameter of the surface" refers to the diameter of a circle formed by the outermost point in the direction of the diameter (the point farthest from the optical axis) when considering the intersections of all rays contributing to image formation and the lens surface diameter. Further, the term "effective diameter edge" refers to the outermost point. When the system is rotationally symmetric about the optical axis, the graph formed by the outermost points is a circle. However, when the system is not rotationally symmetric, in some cases the graph formed by the outermost points is not a circle. In this case, an equivalent circle can be considered, the diameter of which can be regarded as the effective diameter. the

Regarding the shape of the aspheric surface, when the lens surface i of each lens ("i" is a symbol representing the corresponding lens surface. For example, when the object-side surface of the second lens L2 is represented by 3, in the following about the second lens In the description of the object-side surface of L2, "i" can be considered as a point on i=3) is a point Xi, and when the intersection of the normal line and the optical axis at this point is a point Pi, the length Xi-Pi(|Xi- Pi|) is defined as the absolute value of the radius of curvature |RXi| at point Xi, and Pi is defined as the center of curvature at point Xi. Further, the point of intersection of the i-th lens surface and the optical axis is point Qi. At this time, the refractive power at the point Xi is defined based on whether the point Pi is located on the object side or the image side of the point Qi. When point Xi is a point on the object-side surface, if point Pi is located on the image side of point Qi, the refractive power at point Xi is defined as positive refractive power. If the point Pi is located on the object side of the point Qi, the refractive power at Xi is defined as negative refractive power. When point Xi is a point on the image-side surface, if point Pi is located on the object side of point Qi, the refractive power at point Xi is defined as positive refractive power. If the point Pi is located on the image side of the point Qi, the refractive power at Xi is defined as negative refractive power. the

When the refractive power at the center and the refractive power at the point Xi are compared with each other, the absolute value of the radius of curvature (paraxial curvature radius) at the center and the absolute value |RXi| of the radius of curvature at the point Xi are compared with each other. If said value |RXi| is smaller than the absolute value of this paraxial radius of curvature, the refractive power at point Xi is considered to be stronger than that at the center. Conversely, if the value |RXi| is greater than the absolute value of the paraxial radius of curvature, the refractive power at the point Xi is considered to be weaker than that at the center. This relationship is analogous to whether a surface has positive or negative refractive power. the

Here, referring to FIG. 2 , the shape of the object-side surface of second lens L2 will be described. FIG. 2 is a schematic diagram illustrating an optical path of the imaging lens 1 illustrated in FIG. 1 . In FIG. 2 , point Q3 is the center of the object-side surface of second lens L2 , which is an intersection point of the object-side surface of second lens L2 and optical axis Z. In FIG. In FIG. 2 , point X3 on the object-side surface of second lens L2 , which is an intersection of outermost ray 6 included in off-axis ray 3 and the object-side surface of second lens L2 , is located at the effective diameter edge. In Fig. 2, point X3 is located at the effective diameter edge. However, since the point X3 is an arbitrary point on the object-side surface of the second lens, other points can be considered in a similar manner. the

At this time, the intersection of the normal line of the lens surface at point X3 and the optical axis Z is point P3, as shown in Figure 2, and the line segment X3-P3 connecting point X3 and point P3 is defined as the radius of curvature RX3 at point X3 , the length |X3-P3| of the line segment X3-P3 is defined as the absolute value |RX3| of the radius of curvature RX3. In other words, |X3-P3|=|RX3|. Further, the radius of curvature at point Q3, that is, the radius of curvature at the center of the object-side surface of second lens L2 is R3, and the absolute value of this radius of curvature is |R3| (not shown in FIG. 2 ). the

Expressing "the shape of the object-side surface of second lens L2: having positive refractive power both at the center and at the edge of the effective diameter, and when the positive refractive power at the center and the positive refractive power at the edge of the effective diameter are compared with each other , the positive refractive power at the edge of the effective diameter is weaker than that at the center" refers to the following shape: the paraxial region including point Q3 is convex, and point P3 is located at point X3 when point X3 is located at the edge of the effective diameter. The image side of Q3, and the absolute value |RX3| of the radius of curvature at the point X3 is larger than the absolute value |R3| of the radius of curvature at the point Q3. the

The object-side surface of second lens L2 may have a shape having positive refractive power at the center and negative refractive power at the edge of the effective diameter. When the object-side surface of second lens L2 has such a shape, it is possible to reduce the size of the lens system. At the same time, the angle of view can be easily widened. the

The expression "having a shape having positive refractive power at the center and negative refractive power at the edge of the effective diameter" of the object-side surface of second lens L2 means a shape in which the paraxial region including point Q3 is convex, when Point P3 is on the object side of point Q3 while point X3 is at the edge of the effective diameter. the

It is desirable that the object-side surface of second lens L2 has a shape of a portion having negative refractive power at the center and positive refractive power in a region between the center and the edge of the effective diameter. When the object-side surface of second lens L2 has such a shape, it is possible to reduce the size of the lens system and widen the angle of view. At the same time, field curvature can be corrected excellently. the

The expression "shape having a portion having negative refractive power at the center and positive refractive power in the region between the center and the edge of the effective diameter" of the object-side surface of second lens L2 means a shape including the point Q3 The paraxial region is concave, with point X3 located between the center and the edge of the effective diameter with point P3 located on the image side of point Q3. the

The object-side surface of second lens L2 may have a shape having positive refractive power at the center and a portion having positive refractive power in a region between the center and the effective diameter edge and negative refractive power at the effective diameter edge. When the object-side surface of second lens L2 has such a shape, it is possible to reduce the size of the lens system and widen the angle of view. At the same time, field curvature and distortion can be corrected excellently. the

The expression "the shape of the portion having negative refractive power at the center and positive refractive power in the region between the center and the edge of the effective diameter" of the object-side surface of second lens L2 means the following shape: the near The axis region is concave, with point X3 lying between the center and the effective diameter edge with point P3 on the image side of point Q3. Further, the expression "a shape having negative refractive power at the edge of the effective diameter" of the second lens L2 means a shape in which the point P3 is located on the object side of the point Q3 when the point X3 is located at the edge of the effective diameter. the

The object-side surface of second lens L2 may have negative refractive power at both the center and the effective diameter edge, and when the negative refractive power at the center and the negative refractive power at the effective diameter edge are compared with each other, the negative refractive power at the effective diameter edge is The refractive power may be weaker than the shape of negative refractive power at the center. When the object-side surface of second lens L2 has such a shape, it is possible to reduce the size of the lens system and widen the angle of view. At the same time, field curvature can be corrected excellently. the

Expressing the object-side surface of second lens L2 "shape that can have negative refractive power at both the center and the edge of the effective diameter, and when the negative refractive power at the center and the negative refractive power at the edge of the effective diameter are compared with each other, the effective diameter A shape in which the negative refractive power at the edge may be weaker than that at the center" means a shape in which the paraxial region including the point Q3 is concave and the point P3 is at the point Q3 when X3 is at the edge of the effective diameter side, and the absolute value of the radius of curvature |RX3| at the point X3 is greater than the absolute value of the radius of curvature |R3| at the point Q3. the

In FIG. 2 , a circle CQ3 passing through the point Q3 with |R3| as the radius and whose center is a point on the optical axis is drawn with a two-dot dashed line for understanding purposes. Further, a part of the circle CX3 passing through the point X3 with the radius |RX3| passing through the point X3 and whose center is a point on the optical axis is drawn with a dotted line. Circle CX3 is larger than circle CQ3 and clearly illustrates |R3|<|RX3|. the

It is desirable that the image-side surface of second lens L2 is aspherical. Thus, curvature of field and distortion can be excellently corrected. It is desirable that the image-side surface of second lens L2 has a shape having negative refractive power at both the center and the effective diameter, and wherein when the negative refractive power at the center and the negative refractive power at the edge of the effective diameter are compared with each other , the negative power at the effective diameter is weaker than that at the center. When the image-side surface of second lens L2 has such a shape, field curvature and distortion can be excellently corrected. the

The shape of the image-side surface of second lens L2 can be considered as follows in a similar manner to that of the object-side surface of second lens L2 explained with reference to FIG. 2 . In the lens cross section, when a point on the image-side surface of second lens L2 is point X4, and the intersection point between the normal line at that point and the optical axis Z is point P4, the line segment connecting point X4 and point P4 X4-P4 is defined as the radius of curvature at point X4, and the length |X4-P4| of a line segment connecting point X4 and point P4 is defined as the absolute value |RX4| of the radius of curvature at point X4. Therefore, |X4-P4|=|RX4|. Further, the intersection point of the image-side surface of second lens L2 and the optical axis Z, that is, the center of the image-side surface of second lens L2 is point Q4, and the absolute value of the radius of curvature at point Q4 is |R4|. the

The image-side surface of the second lens L2 is expressed as "both have negative refractive power at the center and the effective diameter, and wherein when the negative refractive power at the center and the negative refractive power at the edge of the effective diameter are compared with each other, the negative refractive power at the effective diameter is The "shape in which the refractive power is weaker than the negative refractive power at the center" means a shape in which the paraxial region including the point Q4 is concave, the point P4 is located on the image side of the point Q4 when the point X4 is located at the edge of the effective diameter, and the point The absolute value |RX4| of the radius of curvature at X4 is larger than the absolute value |R4| of the radius of curvature at point Q4. the

It is desirable that the object-side surface of third lens L3 is aspherical. It is desirable that the object-side surface of third lens L3 has a shape having negative refractive power at both the center and the effective diameter, and the negative power at the edge of the effective diameter is weaker than that at the center. Alternatively, it is desirable that the object-side surface of third lens L3 has a shape having negative refractive power at the center and positive refractive power at the edges of the effective diameter. When the object-side surface of third lens L3 has such a shape, coma aberration can be excellently corrected. the

The shape of the object-side surface of third lens L3 can be considered as follows in a similar manner to that of the object-side surface of second lens L2 explained with reference to FIG. 2 . In the lens cross section, when a point on the object-side surface of third lens L3 is point X5, and the intersection point between the normal at that point and the optical axis Z is point P5, the line segment connecting point X5 and point P5 X5-P5 is defined as the radius of curvature at point X5, and the length |X5-P5| of a line segment connecting point X5 and point P5 is defined as the absolute value |RX5| of the radius of curvature at point X5. Therefore, |X5-P5|=|RX5|. Further, the intersection point of the object-side surface of third lens L3 and optical axis Z, that is, the center of the object-side surface of third lens L3 is point Q5, and the absolute value of the radius of curvature at point Q5 is |R5|. the

"A shape that has negative refractive power at both the center and the effective diameter, and the negative power at the edge of the effective diameter is weaker than that at the center" expressing the object-side surface of third lens L3 means the following shapes: The paraxial region of point Q5 is concave, point P5 is located on the object side of point Q5 when point X5 is located at the effective diameter edge, and the absolute value of the radius of curvature |RX5| at point X5 is greater than the absolute value of the radius of curvature at point Q5 Value |R5|. the

Further, the expression "a shape having a negative refractive power at the center and a positive refractive power at the edge of the effective diameter" refers to a shape in which the paraxial region including the point Q5 is concave when the point X5 is located at the edge of the effective diameter Point P5 is located on the image side of point Q5. the

The object-side surface of third lens L3 may have a shape having negative refractive power at both the center and the effective diameter, and wherein when the negative refractive power at the center and the negative power at the edge of the effective diameter are compared with each other, the effective diameter The negative refractive power at the edges is stronger than the negative refractive power at the center. When the object-side surface of third lens L3 has such a shape, it is possible to easily widen the angle of view. Further, it is possible to easily separate axial rays and off-axial rays from each other at first lens L1 and second lens L2. Therefore, curvature of field and distortion can be easily corrected. the

The expression "has negative refractive power at both the center and the effective diameter of the object-side surface of third lens L3, and wherein when the negative refractive power at the center and the negative refractive power at the edge of the effective diameter are compared with each other, the negative refractive power at the edge of the effective diameter is The "shape in which the negative refractive power is stronger than that at the center" means a shape in which the paraxial region including the point Q5 is concave, the point P5 is located on the object side of the point Q5 when the point X5 is located at the edge of the effective diameter, and The absolute value |RX5| of the radius of curvature at the point X5 is smaller than the absolute value |R5| of the radius of curvature at the point Q5. the

A paraxial region on the object-side surface of third lens L3 may be a plane. the

It is desirable that the image-side surface of third lens L3 is aspherical. It is desirable that the image-side surface of third lens L3 has a shape having positive refractive power at both the center and the effective diameter, and in which the positive refractive power at the edge of the effective diameter is weaker than that at the center. When the image-side surface of third lens L3 has such a shape, image quality in the peripheral portion of an image can be improved by excellently correcting coma aberration caused by off-axis rays. the

The shape of the image-side surface of third lens L3 can be considered as follows in a similar manner to that of the object-side surface of second lens L2 explained with reference to FIG. 2 . In the lens cross section, when a point on the image-side surface of third lens L3 is point X6, and the intersection point between the normal line at that point and the optical axis Z is point P6, the line segment connecting point X6 and point P6 X6-P6 is defined as the radius of curvature at point X6, and the length |X6-P6| of a line segment connecting point X6 and point P6 is defined as the absolute value |RX6| of the radius of curvature at point X6. Therefore, |X6-P6|=|RX6|. Further, the intersection of the image-side surface of third lens L3 and optical axis Z, that is, the center of the image-side surface of third lens L3 is point Q6, and the absolute value of the radius of curvature at point Q6 is |R6|. the

"A shape having positive refractive power at both the center and the effective diameter, and in which the positive refractive power at the edge of the effective diameter is weaker than that at the center" expressing the image-side surface of third lens L3 means the following shape: The paraxial region including point Q6 is convex, point P6 is on the object side of point Q6 when point X6 is at the effective diameter edge, and wherein the absolute value of the radius of curvature |RX6| at point X6 is greater than the curvature at point Q6 The absolute value of the radius |R6|. the

The image-side surface of third lens L3 may have a shape having positive refractive power at both the center and the effective diameter edge, and the positive power at the effective diameter edge is stronger than that at the center. When third lens L3 has such a shape, spherical aberration and curvature of field can be easily corrected in an excellent manner. the

The expression "a shape having positive refractive power at both the center and the edge of the effective diameter, and the positive power at the edge of the effective diameter is stronger than that at the center" means a shape in which the paraxial region including the point Q6 is convex From this, point P6 is located on the object side of point Q6 when point X6 is located at the edge of the effective diameter, and wherein the absolute value of the radius of curvature |RX6| at point X6 is smaller than the absolute value of the radius of curvature |R6| at point Q6. the

It is desirable that the object-side surface of sixth lens L6 is aspherical. It is desirable that the object-side surface of sixth lens L6 has a shape that has positive refractive power at both the center and the effective diameter, and the positive refractive power at the edge of the effective diameter is weaker than that at the center. When the object-side surface of sixth lens L6 has such a shape, field curvature and spherical aberration can be easily corrected in an excellent manner. the

The shape of the object-side surface of sixth lens L6 can be considered as follows in a similar manner to that of the object-side surface of second lens L2 explained with reference to FIG. 2 . In the lens cross section, when a point on the object-side surface of sixth lens L6 is point X12, and the intersection point between the normal line at that point and the optical axis Z is point P12, the line segment connecting point X12 and point P12 X12-P12 is defined as the radius of curvature at point X12, and the length |X12-P12| of a line segment connecting point X12 and point P12 is defined as the absolute value |RX12| of the radius of curvature at point X12. Therefore, |X12-P12|=|RX12|. Further, the intersection of the object-side surface of sixth lens L6 and optical axis Z, that is, the center of the object-side surface of sixth lens L6 is point Q12, and the absolute value of the radius of curvature at point Q12 is |R12|. the

The expression "a shape having positive refractive power at both the center and the effective diameter, and the positive refractive power at the edge of the effective diameter being weaker than that at the center" of the object-side surface of sixth lens L6 means the following shapes: The paraxial region of point Q12 is convex, point P12 is located on the image side of point Q12 when point X12 is located at the effective diameter edge, and wherein the absolute value of the radius of curvature |RX12| at point X12 is larger than the radius of curvature at point Q12 The absolute value of |R12|. the

It is desirable that the image-side surface of sixth lens L6 is aspherical. It is desirable that the image-side surface of sixth lens L6 has a shape that has positive refractive power both at the center and at the edge of the effective diameter, and the positive refractive power at the edge of the effective diameter is weaker than that at the center, or has a shape at the center. Positive refractive power and shapes with negative refractive power at the edge of the effective diameter. When the image-side surface of sixth lens L6 has such a shape, spherical aberration and field curvature can be excellently corrected. the

The shape of the image-side surface of sixth lens L6 can be considered as follows in a similar manner to that of the object-side surface of second lens L2 explained with reference to FIG. 2 . In the lens cross section, when a point on the image-side surface of sixth lens L6 is point X13, and the intersection point between the normal line at that point and the optical axis Z is point P13, the line segment connecting point X13 and point P13 X13-P13 is defined as the radius of curvature at point X13, and the length |X13-P13| of a line segment connecting point X13 and point P13 is defined as the absolute value |RX13| of the radius of curvature at point X13. Therefore, |X13-P13|=|RX13|. Further, the intersection of the image-side surface of sixth lens L6 and optical axis Z, that is, the center of the image-side surface of sixth lens L6 is point Q13, and the absolute value of the radius of curvature at point Q13 is |R13|. the

The expression “a shape having positive refractive power at both the center and the edge of the effective diameter, and the positive refractive power at the edge of the effective diameter being weaker compared with the center” of the image-side surface of sixth lens L6 refers to shapes including The paraxial region of the point Q13 is convex, and the point P13 is located on the object side of the point Q13 when the point X13 is located at the edge of the effective diameter, and wherein the absolute value of the radius of curvature 1RX13| at the point X13 is larger than the radius of curvature at the point Q13 The absolute value of |R13|. the

Further, the expression "a shape having a positive refractive power at the center and a negative refractive power at the edge of the effective diameter" refers to a shape in which the paraxial region including the point Q13 is convex when the point X13 is located at the edge of the effective diameter The time point P13 is located on the image side of the point Q13. the

When each of the object-side surface of second lens L2 to the image-side surface of sixth lens L6 has the above-described aspherical shape, distortion can be excellently corrected in addition to spherical aberration, field curvature, and coma aberration . the

It is desirable that first lens L1 is a meniscus lens having a convex surface facing the object side. Thus, it becomes possible to produce lenses with a wide field of view, for example, exceeding 180 degrees. When first lens L1 is a biconcave lens, the refractive power of first lens L1 can be easily increased. Therefore, it is possible to easily widen the angle of view. However, the light rays are sharply bent by the first lens L1. Therefore, correction of distortion becomes difficult. Further, when the object-side surface is concave, the incident angle of peripheral rays entering the lens surface becomes large. Therefore, when light enters the surface, the reflection loss becomes large. Thus, the peripheral area becomes dark. Further, when the incident angle of light exceeds 180 degrees, the light cannot enter the surface. Therefore, it is desirable that first lens L1 is a positive meniscus lens having a convex surface facing the object side in order to easily correct distortion while realizing a wide angle of view. the

It is desirable that second lens L2 is a biconcave lens. Thus, it becomes possible to easily widen the angle of view, and to easily correct curvature of field, distortion, and spherical aberration. the

The second lens L2 may be a meniscus lens having a convex surface facing the object side. Thus, it is possible to easily widen the angle of view, and excellently correct distortion and curvature of field. the

It is desirable that the object-side surface of third lens L3 is concave or flat. Thus, the angle of view can be easily widened, and paraxial rays and peripheral rays can be easily separated from each other at the first lens L1 and the second lens L2. Therefore, field curvature and coma aberration can be excellently corrected. the

It is desirable that the image-side surface of third lens L3 is convex. Thus, the refractive power of third lens L3 can be made to be positive refractive power, and lateral chromatic aberration can be excellently corrected. the

It is desirable that third lens L3 includes a meniscus shape with a concave surface facing the object side, or a plano-convex lens with a flat surface facing the object side. Thus, it is possible to easily reduce the size of the lens system in the direction of the system, and excellently correct curvature of field and coma aberration. the

It is desirable that fourth lens L4 is a biconvex lens. Thus, spherical aberration and curvature of field can be corrected excellently. Further, when the refractive power of fourth lens L4 is increased, chromatic aberration between fourth lens L4 and fifth lens L5 can be easily corrected. the

It is desirable that fifth lens L5 is a biconcave lens or a plano-convex lens having a plane facing the image side. Therefore, curvature of field can be corrected excellently. Further, the refractive power of fifth lens L5 can be easily increased, and chromatic aberration between fourth lens L4 and fifth lens L5 can be easily corrected. the

Fifth lens L5 may be a negative meniscus lens having a convex surface facing the image side, or a plano-concave lens having a flat surface facing the image side. Thus, coma aberration and curvature of field can be easily corrected in an excellent manner. the

It is desirable that sixth lens L6 is a biconvex lens. Thus, the angle at which light enters the imaging device can be suppressed. Therefore, shading can be easily suppressed. the

Sixth lens L6 may be a meniscus lens having a convex surface facing the image side. Thus, curvature of field can be easily corrected in an excellent manner. the

It is desirable that the material of first lens L1 is glass. When the imaging lens is used in harsh environmental conditions, for example, as used in an in-vehicle camera or a surveillance camera, the first lens L1 disposed on the closest object side needs to be designed to resist deterioration of the surface by wind and rain and temperature changes caused by direct sunlight. , and materials that are resistant to chemicals such as grease and detergents. In other words, the material needs to be highly water-resistant, temperature-resistant, acid-resistant, chemical-resistant, etc. Further, in some cases, the material needs to be hard and not easily broken. These requirements can be satisfied if the material of the first lens L1 is glass. Alternatively, transparent ceramics may be used as the material of the first lens L1. Further, as a material of the first lens L1, a material having a Knoop hardness of 550 or higher may be used. It is desirable that the material of the first lens L1 has acid resistance of rank 4 or higher by the powder method and has Water resistance of grade 3 or higher, and higher grades are more desirable. Further, it is desirable that the material has a detergent resistance of class 3 or higher as specified by ISO. Further, it is desirable that the material has weather resistance of grade 3 or higher in terms of the surface method. Further, for example, lenses used for in-vehicle cameras or surveillance cameras are exposed to ultraviolet rays from the sun for a long time. Therefore, it is desirable to use an ultraviolet-resistant material as the material of the lens. the

One or both surfaces of first lens L1 may be aspherical. When the first lens L1 is a glass aspherical lens, various aberrations can be corrected more excellently. the

Further, a protector may be applied to the object-side surface of the first lens L1 to enhance the strength, scratch resistance, and chemical resistance of the surface. In this case, the material of the first lens L1 may be plastic. This protective device can be a hard coat or a waterproof coating. the

It is desirable that the material of one of second lens L2, third lens L3, and sixth lens L6, or a combination of arbitrary plural lenses among them, is plastic. When the material is plastic, the lens system can be constructed at low cost and light weight. Further, when an aspheric surface is provided, an aspheric shape can be precisely produced. Therefore, it is possible to manufacture a lens with excellent performance. the

A material of at least one of the fourth lens L4 and the fifth lens L5 may be plastic. When the material is plastic, the lens system can be constructed at low cost and light weight. Further, when an aspheric surface is provided, an aspheric shape can be precisely produced. Therefore, it is possible to manufacture a lens with excellent performance. the

It is desirable that the material of second lens L2 and sixth lens L6 is polyolefin. Polyolefins can yield materials with low water absorption, high transparency, low birefringence, and large Abbe numbers. When the material of second lens L2 and sixth lens L6 is polyolefin, it is possible to manufacture a lens whose shape changes due to water absorption is small and which has high transmittance and low birefringence. Further, a material having a large Abbe number can be used. Therefore, the occurrence of longitudinal chromatic aberration and lateral chromatic aberration can be suppressed. Further, a highly environment-resistant lens with excellent resolution performance can be manufactured. the

It is desirable that the material of third lens L3 is polycarbonate. Polycarbonate has a small Abbe number. When polycarbonate is used in third lens L3, lateral chromatic aberration can be excellently corrected. the

The material of the second lens L2 and the sixth lens L6 may be acrylic resin. Since acrylic resin is cheap, the cost of the lens system can be reduced by using acrylic resin. the

A so-called nanocomposite material in which particles smaller than the wavelength of light are mixed into the plastic when the plastic material is in at least one of the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6 can be used as this material. the

A material of one of the second lens L2, the third lens L3, and the sixth lens L6, or a material of a combination of any of them may be glass. When the material is glass, performance deterioration caused by temperature changes can be suppressed. the

It is desirable that the material of at least one of fourth lens L4 and fifth lens L5 is glass. When the material of fourth lens L4 is glass, performance deterioration caused by temperature changes can be suppressed. When the material of fifth lens L5 is glass, a material having a small Abbe number can be easily selected. Therefore, chromatic aberration can be easily corrected. the

It is desirable that the glass transition temperature (Tg) of the material of at least one of the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6 is higher than or equal to 145. C, and higher than or equal to 150. A glass transition temperature of C is more desirable. When used its glass transition temperature is higher than or equal to 150. C, it is possible to manufacture lenses with excellent heat resistance. the

Further, based on the purpose of the imaging lens 1 , a filter that cuts off ultraviolet light to blue light, or an IR (infrared) cut filter that cuts off infrared light, may be inserted between the lens system and the imaging device 5 . Alternatively, a coating having characteristics similar to those of the aforementioned optical filter may be applied to the lens surface, or a material that absorbs ultraviolet light, blue light, infrared light, etc. may be used as a material of one lens. the

FIG. 1 illustrates a case in which optical members PP assumed to be various filters and the like are provided between the lens system and the imaging device 5 . Instead, various filters may be provided between the lenses. Alternatively, a coating having the same effect as various filters may be applied to the lens surface of one lens included in the imaging lens. the

Here, light passing outside the effective diameter between the lenses may become stray light and reach the image plane. Further, stray light may become a ghost. Therefore, it is desirable, if necessary, to provide light shielding means for blocking stray light. For example, the light shielding means can be provided by applying opaque varnish to the portion of the lens outside the effective diameter, or by providing an opaque plate member there. Alternatively, an opaque plate member as light shielding means may be provided in the optical path of light rays that will become stray light. Alternatively, a cover member for blocking stray light may also be provided on the object side closest to the object side lens. FIG. 1 illustrates an example in which light-shielding means 11 , 12 are provided outside the effective diameters on the image-side surface of first lens L1 and the image-side surface of second lens L2 , respectively. The position where the light shielding device is provided is not limited to the example illustrated in FIG. 1 . The light shielding means may be provided on the other lens or between the lenses. the

Further, a member such as a stop may be provided between the lenses to block peripheral rays in such a manner that the relative illuminance is within a practically acceptable range. A peripheral ray is a ray that comes from an object point not located on the optical axis Z and passes through the peripheral portion of the entrance pupil of the optical system. When the member that blocks peripheral light is provided in this way, image quality in the peripheral portion of the image forming region can be improved. Further, the member reduces ghosting by blocking light that produces ghosting. the

In the imaging lenses according to the first to fifth embodiments, it is desirable that the lens system consists of only the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6 consists of six lenses. When the lens system is composed of only six lenses, the cost of the lens system can be reduced. the

An imaging device according to an embodiment of the present invention includes an imaging lens according to an embodiment of the present invention. Therefore, an imaging device can be constructed with a small size and low cost. Further, the imaging device has a sufficiently wide angle of view, and high-quality images with high resolution can be obtained by employing the imaging device. the

Images obtained by shooting with the imaging device including the imaging lens according to the first to fifth embodiments can be displayed on the portable phone. For example, a photographing apparatus including an imaging lens according to an embodiment of the present invention is installed in an automobile as an in-vehicle camera in some cases. Further, the rear side of the car or the surrounding area of the car is photographed by the in-vehicle camera, and an image obtained by photographing is displayed on the display device. In this case, if a car navigation system (hereinafter, referred to as a car navigation) is installed in a car, images obtained by photographing can be displayed on a display device of the car navigation. However, if the car navigation is not installed in the car, a dedicated display device, such as a liquid crystal display, needs to be set in the car. However, display devices are expensive. Meanwhile, in recent years, high-performance display devices that can be used to browse moving images and web pages have become mounted on cellular phones. If a cellular phone is used as a display device for an in-vehicle camera, there is no need to install a dedicated display device in the car even if car navigation is not installed in the car. Therefore, the in-vehicle camera can be installed at low cost. the

Here, an image obtained by photographing by an in-vehicle camera can be wired to a cellular phone by using a cable. Alternatively, the image may be wirelessly transmitted to the cellular phone through infrared communication or the like. Further, the operation of the cellular phone or the like and the operation of the car can be associated with each other. When the car is in reverse gear, the image obtained by the in-car camera can be automatically displayed on the display device of the cellular phone. the

A display device for displaying an image obtained by an in-vehicle camera is not limited to a cellular phone. A mobile information terminal that can be carried by a user, such as a PDA, a small-sized personal computer, or a small-sized car navigation can be used. the

[Numerical example of imaging lens]

Next, numerical examples of the imaging lens of the present invention will be described. Lens cross-sections of the imaging lenses of Examples 1 to 19 are illustrated in FIGS. 3 to 21 , respectively. In FIGS. 3 to 21 , the left side of the diagram is the object side, and the right side of the diagram is the image side. Further, the aperture stop St, the optical member PP, and the imaging device 5 disposed on the image plane Sim are also illustrated in a similar manner to FIG. 1 . In each schematic diagram, the aperture stop St does not indicate the shape or size of the aperture stop St, but indicates the position of the aperture stop St on the optical axis Z. In each example, symbols Ri, Di (i=1, 2, 3, . . . ) in the lens cross section correspond to Ri, Di of lens data to be described next. the

The imaging lens according to the first embodiment of the present invention corresponds to Examples 1 to 19. The imaging lens according to the second embodiment of the present invention corresponds to Examples 1-3 and 5 to 19. An imaging lens according to a third embodiment of the present invention corresponds to Examples 1 to 3 and 5 to 19. An imaging lens according to a fourth embodiment of the present invention corresponds to Examples 1 to 4 and 6 to 19. An imaging lens according to a fifth embodiment of the present invention corresponds to Examples 1 to 3 and 6 to 19. the

Tables 1 to 19 show lens data about the imaging lenses of Examples 1 to 19, respectively. In each table, (A) shows basic lens data, (B) shows various data, and (C) shows aspherical surface data. the

In the basic lens data, the Si column shows the surface number of the i-th (i=1, 2, 3, . . . ) surface. The surface number of the object-side surface of the constituent elements closest to the object side is the first surface, and the surface numbers sequentially increase toward the image side. The column of Ri shows the radius of curvature of the i-th surface, and the column of Di shows the distance on the optical axis Z between the i-th surface and the (i+1)-th surface. Here, the sign of the radius of curvature is positive when the shape of the surface is convex toward the object side, and negative when the shape of the surface is convex toward the image side. Further, the Ndj column shows the refractive index of the j-th (j=1, 2, 3, . . . ) light source element with respect to the d-line (wavelength is 587.6 nm). The lens closest to the object side is the first optical element, and the number j increases sequentially toward the image side. The vdj column shows the Abbe number of the jth component element with respect to the d-line. Here, the basic lens data includes aperture stop St and optical member PP. In the column of the surface number, the term "(St)" is also written for the surface corresponding to the aperture stop St. the

In the basic lens data, a mark "*" is attached to the surface number of the aspheric surface. The basic lens data shows the numerical value of the paraxial curvature radius (curvature radius at the center) as the curvature radius of the aspheric surface. The aspheric surface data shows the surface number of the aspheric surface and the aspheric surface coefficient of the aspheric surface. In the aspheric surface data, "En (n: integer)" means "×10 ^-n ", and "E+n" means "×10 ⁿ ". The aspheric surface coefficient is the value of KA, RB _m (m=3, 4, 5,...20) in the following aspheric formula:

[Formula 1]

$Z=\frac{C\&times;Y^2}{1+\sqrt{1-\mathrm{KA}\&times;C^2\&times;Y^2}}+\underset{m}{\mathrm{\&Sigma;}}{\mathrm{RB}}_m{Y}^m$ ,in

Zd: Depth of the aspheric surface (vertical length from a point with height Y on the aspheric surface to a plane touching the apex of the aspheric surface and perpendicular to the optical axis),

Y: height (length from optical axis to lens surface),

C: paraxial curvature, and

KA, RB _m : Aspherical coefficient (m=3, 4, 5...20).

Among the various data, L is the distance from the object-side surface of the first lens L1 to the image plane Sim on the optical axis Z (the back focus part is the distance in the air), and Bf is the distance from the lens closest to the image side on the optical axis Z The distance from the side surface of the image to the image plane Sim (corresponding to the back focus, and the distance in the air). Further, f is the focal length of the entire system, f1 is the focal length of the first lens L1, f2 is the focal length of the second lens L2, f3 is the focal length of the third lens L3, f4 is the focal length of the fourth lens L4, and f5 is the fifth lens The focal length of L5, f6 is the focal length of the sixth lens L6. Further, f23 is a combined focal length of second lens L2 and third lens L3, and f45 is a combined focal length of fourth lens L4 and fifth lens L5. the

Tables 20 and 21 collectively show the values of the conditional formulas corresponding to each example. Here, conditional formula (1) is (R8+R9)/(R8-R9), conditional formula (2) is D9/f, conditional formula (3) is (R5+R6)/(R5-R6), conditional Formula (4) is (R10+R11)/(R10-R11), conditional formula (5) is D4/f, conditional formula (6) is vd3+vd5, conditional formula (7) is |f1/f|, condition Formula (8) is |t2/f|, conditional formula (9) is f3/f, conditional formula (10) is f4/f, conditional formula (11) is R2/f, conditional formula (12) is R9/f , conditional formula (13) is R1/f, conditional formula (14) is f6/f, conditional formula (15) is R13/f, conditional formula (16) is f5/f, conditional formula (17) is R4/f , conditional formula (18) is R10/f, conditional formula (19) is (D4+D5)/f, conditional formula (20) is f/R5, conditional formula (21) is f/R3, conditional formula (22) is f23/f, conditional formula (23) is f45/f, conditional formula (24) is L/f, conditional formula (25) is Bf/f, conditional formula (26) is (R1+R2)/(R1- R2), where

R1: radius of curvature of the object-side surface of the first lens L1,

R2: radius of curvature of the image side surface of the first lens L1,

R3: radius of curvature of the object-side surface of the second lens L2,

R4: radius of curvature of the image side surface of the second lens L2,

R5: the radius of curvature of the object-side surface of the third lens L3,

R6: radius of curvature of the image side surface of the third lens L3,

R8: radius of curvature of the object-side surface of the fourth lens L4,

R9: radius of curvature of the image side surface of the fourth lens L4,

R10: the radius of curvature of the object-side surface of the fifth lens L5,

R11: radius of curvature of the image side surface of the fifth lens L5,

R13: the radius of curvature of the image side surface of the sixth lens L6,

D4: The air gap on the optical axis between the second lens L2 and the third lens L3,

D5: the central thickness of the third lens L3,

D9: the air gap between the fourth lens L4 and the fifth lens L5 on the optical axis,

vd3: the Abbe number of the material of the third lens L3 with respect to the d line,

vd5: the Abbe number of the material of the fifth lens L5 with respect to the d line,

f: focal length of the whole system,

f1: the focal length of the first lens L1,

f2: the focal length of the second lens L2,

f3: focal length of the third lens L3,

f4: the focal length of the fourth lens L4,

f5: the focal length of the fifth lens L5,

f6: focal length of the sixth lens L6,

f23: the combined focal length of the second lens L2 and the third lens L3,

f45: Combined focal length of the fourth lens L4 and the fifth lens L5

L: the length from the object-side surface of the first lens L1 to the image plane Sim on the optical axis (the back focus part is the distance in the air), and

Bf: the length on the optical axis from the image-side surface of the lens closest to the image-side to the image plane Sim (distance in air). the

As the unit of each numerical value, "mm" is used for the length. However, this unit is merely an example. Since the optical system can be utilized by scaling the optical system up or down, other suitable units can be used. the

In the imaging lenses of Examples 1 to 19, the first lens L1, the fourth lens L4, and the fifth lens L5 are glass spherical lenses, and the second lens L2, third lens L3, and sixth lens L6 are plastic aspheric lenses. the

In Fig. 22(A) to Fig. 22(D), Fig. 23(A) to Fig. 23(D), Fig. 24(A) to Fig. 24(D), Fig. 25(A) to Fig. 25(D), Fig. 26(A) to 26(D), 27(A) to 27(D), 28(A) to 28(D), 29(A) to 29(D), 30( A) to Figure 30(D), Figure 31(A) to Figure 31(D), Figure 32(A) to Figure 32(D), Figure 33(A) to Figure 33(D), Figure 34(A) To Fig. 34(D), Fig. 35(A) to Fig. 35(D), Fig. 36(A) to Fig. 36(D), Fig. 37(A) to Fig. 37(D), Fig. 38(A) to Fig. 38(D), FIGS. 39(A) to 39(D), and FIGS. 40(A) to 40(D) illustrate aberration diagrams of the imaging lenses according to Examples 1 to 19, respectively. the

Here, the aberration diagram of Example 1 will be explained as an example, but the aberration diagrams of other examples are similar to that of Example 1. 22(A), FIG. 22(B), FIG. 22(C) and FIG. 22(D) respectively illustrate spherical aberration, astigmatism, distortion (distortion aberration) and lateral chromatic image in the imaging lens of Example 1 Poor (chromatic aberration of magnification). In the schematic diagrams of spherical aberration, F represents the F-number, and in other schematic diagrams, ω represents the half angle of view. In the schematic diagram of distortion, by taking the focal length f and field angle of the whole system (variable, ), indicating the height from the ideal image offset. Each aberration schematic diagram illustrates the aberration at the reference wavelength of d-line (587.56nm). The schematic diagram of spherical aberration also illustrates aberrations with respect to F-line (wavelength 486.13 nm), C-line (wavelength 656.27 nm), and the amount of violation of the sinusoidal condition (indicated by SNC). Further, schematic diagrams of lateral chromatic aberrations illustrate aberrations with respect to F-line and C-line. Since the kind of lines used in the lateral chromatic aberration is the same as that used in the schematic diagram of the spherical aberration, description will be omitted in the schematic diagram of the lateral chromatic aberration.

As shown by these data, the imaging lenses of Examples 1 to 19 are composed of six lenses which are a small number of lenses, and can be manufactured in a small size and at low cost. Further, an extremely wide viewing angle with a full viewing angle of about 178 to 208 degrees can be realized. Further, the F-number is 2.0, which is small. Further, the imaging lens has excellent optical performance in which each aberration has been corrected in an excellent manner. These imaging lenses are suitably used in surveillance cameras, in-vehicle cameras, and the like that image images for images on the front side, lateral side, rear side, and the like of a car. the

[Example of imaging device]

As a usage example, FIG. 41 illustrates a manner in which an imaging device including an imaging lens according to an embodiment of the present invention is installed in a car 100. In FIG. 41 , a car 100 includes an exterior camera 101 for imaging the driver's blind spot near the driver's side of the seat, an exterior camera 102 for imaging the driver's blind spot on the rear side of the car 100, and The internal camera 103 images the same range as the driver's field of vision. The interior camera 103 is attached to the rear side of the rearview mirror. The external camera 101, the external camera 102, and the internal camera 103 are imaging devices according to one embodiment of the present invention, and they include an imaging lens according to one example of the present invention and a device for converting an optical image formed by the imaging lens into an electrical signal imaging device. the

The imaging lens according to this example of the present invention has the aforementioned advantages. Therefore, the external cameras 101 and 102, and the internal camera 103 are also constructed in a small size and low cost, and have a wide angle of view. Further, they can obtain high-quality images even in the peripheral portion of the image forming region. the

So far, the present invention has been described by using the embodiments and examples. However, the present invention is not limited to the above-mentioned embodiments and examples, and various modifications are possible. For example, the values of the radius of curvature, surface pitch, refractive index, and Abbe's number of each lens element are not limited to those in the aforementioned numerical examples, but may be other values. the

In the preceding examples, all lenses were constructed of homogenous material. Alternatively, a gradient index lens with a refractive index profile may be used. Further, in some of the aforementioned examples, second lens L2 to sixth lens L6 are constituted by refractive type lenses on which aspherical surfaces are formed. A diffractive optical element or elements may be formed on a surface or on multiple surfaces. the

In the embodiment of the imaging device, a case in which the present invention is applied to an in-vehicle camera is described with reference to the drawings. However, the use of the present invention is not limited to this purpose. For example, the present invention can be applied to cameras for mobile terminals, surveillance cameras, and the like. the

Claims (17)

1. An imaging lens basically consists of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, a negative fifth lens, and a positive sixth lens set sequentially from the object side Lens These six lenses constitute, It is characterized in that, Satisfy the following conditions formulas (1) and (6): -0.11<(R8+R9)/(R8-R9)<0.44...(1); and 38.1＜vd3+vd5＜45.1...(6), where R8: radius of curvature of the object-side surface of the fourth lens, R9: radius of curvature of the image side surface of the fourth lens, vd3: the Abbe number of the material of the third lens with respect to the d-line, and vd5: the Abbe number of the material of the fifth lens with respect to the d line. the 2. An imaging lens basically consists of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, a negative fifth lens, and a positive sixth lens set sequentially from the object side. Lens These six lenses constitute, It is characterized in that, The materials of the first lens, the second lens, the fourth lens and the sixth lens have an Abbe number with respect to the d-line greater than or equal to 40, and Wherein the following conditional formulas (1-1) and (12) are satisfied: -0.11<(R8+R9)/(R8-R9)...(1-1); and R9/f＜-2.9...(12), where R8: radius of curvature of the object-side surface of the fourth lens, R9: the radius of curvature of the image-side surface of the fourth lens, and f: focal length of the whole system. the 3. An imaging lens basically consists of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, a negative fifth lens, and a positive sixth lens set sequentially from the object side. Lens These six lenses constitute, It is characterized in that, The Abbe number of the material of the first lens, the second lens, the fourth lens and the sixth lens with respect to the d-line is greater than or equal to 40, and Wherein the following conditional formulas (1-2) and (4) are met: -0.075<(R8+R9)/(R8-R9)<0.11...(1-2); and -1.04＜(R10+R11)/(R10-R11)＜-0.34...(4), where R8: radius of curvature of the object-side surface of the fourth lens, R9: radius of curvature of the image side surface of the fourth lens, R10: the radius of curvature of the object-side surface of the fifth lens, and R11: radius of curvature of the image-side surface of the fifth lens. the 4. An imaging lens basically consists of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, a negative fifth lens, and a positive sixth lens set sequentially from the object side. Lens These six lenses constitute, It is characterized in that, The object-side surface of the third lens is concave, and wherein the Abbe number of the materials of the first lens, the second lens, the fourth lens and the sixth lens with respect to the d-line is greater than or equal to 40, and Wherein when the Abbe number of the material of the first lens with respect to the d-line is vd1, and the Abbe number of the material of the third lens with respect to the d-line is vd3, vd1/vd3 is greater than or equal to 1.4 and less than or equal to 2.5, and Wherein the following conditional formulas (1-3) and (4-1) are satisfied: (R8+R9)/(R8-R9)<0.17...(1-3); and (R10+R11)/(R10-R11)＜-0.35...(4-1), where R8: radius of curvature of the object-side surface of the fourth lens, R9: radius of curvature of the image side surface of the fourth lens, R10: the radius of curvature of the object-side surface of the fifth lens, and R11: radius of curvature of the image-side surface of the fifth lens. the 5. imaging lens according to claim 4, is characterized in that, wherein the object-side surface of the third lens is concave, and where the fourth lens is a biconvex lens, and where the fifth lens is a biconcave lens, and Wherein the following conditional formulas (1-3) and (4-1) are satisfied: (R8+R9)/(R8-R9)<0.17...(1-3); and (R10+R11)/(R10-R11)＜-0.35...(4-1), where R8: radius of curvature of the object-side surface of the fourth lens, R9: radius of curvature of the image side surface of the fourth lens, R10: the radius of curvature of the object-side surface of the fifth lens, and R11: radius of curvature of the image-side surface of the fifth lens. the 6. The imaging lens according to any one of claims 1-4, characterized in that, the following conditional formula (19) is satisfied: 1<(D4+D5)/f<6...(19), where D4: the air gap between the second lens and the third lens on the optical axis, D5: the central thickness of the third lens, and f: focal length of the whole system. the 7. The imaging lens according to claim 6, wherein the following conditional formula (19-3) is satisfied: 1.9＜(D4+D5)/f＜4.4...(19-3), where D4: the air gap between the second lens and the third lens on the optical axis, D5: the central thickness of the third lens, and f: focal length of the whole system. the 8. The imaging lens according to any one of claims 1-4, characterized in that, the following conditional formula (20) is satisfied: -1<f/R5<1...(20), where f: the focal length of the entire system, and R5: radius of curvature of the object-side surface of the third lens. the 9. The imaging lens according to claim 8, characterized in that, the following conditional formula (20-2) is satisfied: -0.5＜f/R5＜0.5...(20-2), where f: the focal length of the entire system, and R5: radius of curvature of the object-side surface of the third lens. the 10. The imaging lens according to any one of claims 1-4, characterized in that, the following conditional formula (21) is satisfied: -3<f/R3<3...(21), where f: the focal length of the entire system, and R3: radius of curvature of the object-side surface of the second lens. the 11. The imaging lens according to claim 10, characterized in that, the following conditional formula (21-2) is satisfied: -2.0＜f/R3＜1.5...(21-2), where f: the focal length of the entire system, and R3: radius of curvature of the object-side surface of the second lens. the 12. The imaging lens according to any one of claims 1-4, characterized in that, the following conditional formula (22) is satisfied: -30＜f23/f＜-3...(22), where f23: the combined focal length of the second and third lenses, and f: focal length of the whole system. the 13. The imaging lens according to claim 12, characterized in that, the following conditional formula (22-2) is satisfied: -20＜f23/f＜-5...(22-2), where f23: the combined focal length of the second and third lenses, and f: focal length of the whole system. the 14. The imaging lens according to any one of claims 1-4, characterized in that, the following conditional formula (23) is satisfied: 2＜f45/f＜25...(23), where f45: the combined focal length of the fourth and fifth lenses, and f: focal length of the whole system. the 15. The imaging lens according to claim 14, characterized in that, the following conditional formula (23-2) is satisfied: 4＜f45/f＜20...(23-2), where f45: the combined focal length of the fourth and fifth lenses, and f: focal length of the whole system. the 16. The imaging lens according to any one of claims 1-4, characterized in that the diaphragm is disposed between the third lens and the fourth lens. the 17. An imaging device, characterized in that, comprising: The imaging lens according to any one of claims 1-16 installed on the imaging device. the